There has been obtained and is being maintained in vitro for over 12 years a stable cellular line DAPT, derived from a dedifferentiated human astrocytoma. In monolayer cultures the cells have passed 270 times. During 22 month (63 passages) the cells had a fibroblast-like shape, their growth having thereafter assumed an epithelioid character. On being impregnated with chlorous gold after Ramon-and-Kachal the cellular cytoplasma is stained purple-violet. In the periods of the fibroblast-like and epithelioid growth the time of the population doubling was 145 and 74 hours, respectively. The mitotic index amounted to 18%. When investigated during the 3d (106th passage) and 11th (250th passage) years of its cultivation the population consisted largely of cells containing 60-65 chromosomes. The carotype of the DAPT cells retained the main traits common to the structure of the human caryotype. After 7-9 months of cultivation (16-25th passages) the DAPT cells demonstrated the presence therein of an active glutamineketoacidic aminotransferase. Further on the activity of the enzyme declined. Factors influencing the changeability of the stable cellular DAPT line are discussed.

When studying the Q-, G-, and C-bands, the character of acrocentric chromosomes' bands was found to be varying even within the same tumor. However, the bands of the markerchromosomes A and B coincide in NK/Ly and in the Ehrlich--Lettres tumors. With the aid of staining for revealing C-bands, the acrocentric markers "cc" and "ac" common for both tumors, were first noted. This corroborates the opinion of the replacement of NK/Ly by the Ehrlice-Lettres tumor.

Malignant tumors and pre-cancer processes are characterized by a high proliferative activity of cells, high chromosome variability and extremely high genome variability which is 10 times, as high as that in non-tumor actively proliferating tissues. A clear positive correlation is found between the cell division rate and the level of chromosome variability.

The age of leucosis disease of cattle was found to be 6,5 years on the basis of the materials collected on seven State farms. The probability of the disease in young animals was found to be low, and it increased in adult cows. The size of population and the percentage of purebred in herd did not influence on the frequency of the disease. Highly productive animals were mostly exposed to the disease, while healthy and diseased animals exerted no differences in the fat content of milk.

A survey of the latest data associated with the analysis of the mechanisms of cancerogenesis with the help of hybridization of somatic cells is presented. Results of the investigations showing that malignization is not a dominant feature are discussed. A possible role of hybridization of cells in vivo in the genesis of tumours is indicated.

It has been found that females with dyshormonal tumors can be divided into two groups as to the incidence of sex chromatin in buccal mucosa. An existance of two groups differentiated by the sex chromatin incidence was also supported by the data obtained during examination of apparently healthy females of child-bearing age. The relationship has been established between the incidence of sex chromatin and certain features of the reproductive function. It may be assumed that the female population consists of two subgroups differentiated by a constitutional type of hormonal balance. Some evidences on population heterogeneity as concerns the factors determining the incidence of sex chromatin were obtained in studies of the latter conducted in males. We may suggest, therefore, the relationship between the two variants of dyshormonal tumors and two constitutional types of ageing.

Chromosome abberations in cells of 4 ovarian cancer patients have been studied prior to and during the treatment with ThioTEPA. ThioTEPA was injected intraperitoneally once a week in a dose of 40 mg. The amount of abberant cells prior to the therapy averaged 7.8%. 14 days following the treatment the amount of cells with chromosome abberations reached its peak (88.6%). By the 21st day of ThioTEPA treatment, when a total dose of the drug was 120 mg, the number of cells with abberations rapidly decreased, and by the 28-35th day of treatment there was a fall up to the initial values. ThioTEPA induced in tumor cells chiefly abberations of chromatoid type that evidenced the injury of cells in a phase G2 of the cellular cycle. A decrease in the number of chromosome abberations in tumor cells during the treatment with chemotherapeutic drugs is a morphological indication of the appearance of drug resistance.

The author presents a classification and descriptions of various forms of pathology of mitosis. Changes in the mitotic regimen following administration of some drugs and under the effect of extreme factors are considered. Data on changes in the number and character of pathological mitoses in viral infection and radiation damage are discussed. Particular attention is given to the analysis of shifts in the mitotic regimen in various benign and malignant hyperplasia. It is shown that malignization (precancer and cancer of the larynx, endometrium, cervix uteri and stomach) is characterized by a rise of the mitotic activity, detection of division in metaphase and by a drastic increase in the number of pathological mitoses. These indices are used in the differential diagnosis of neoplastic processes and for early detection of possible malignization pf precancer hyperplasia.

At the age of scientific and technical progress and of industrialization of animal husbandry neither theoretical nor applied science can dispense with the data of the veterinary genetics. Unfortunately this branch of science does not receive the attention it deserves. The following three problems have to be solved by the veterinary genetics: (1) the investigation of the relationship between the heredity and the pathology of animals; the examination of the mechanism of pathology at the molecular and organism genetic levels; (2) the elaboration of the methods of genetic diagnostics; (3) the search for scientifically-substantiated directions in breeding of animal breeds highly resistant to diseases. The main attention will be paid to the investigation of the mechanisms ensuring the natural resistance of animals to certain definite diseases. The establishment and development of veterinary genetics will exert a favourable influence on the progress of biological sciences. Its data will be indispensable both for the theory and the practice of agriculture.

A review of recent advances in genetics of somatic cells is given in the article. It contains three sections: 1) hybridization of somatic cells and its application to the mapping of genes and to the study of gene action; 2) relation of somatic cell genetics to genetic engineerings; 3) progress and perspectives of higher plant somatic cell genetics.