402 SUMMARY OF CURRENT RESEARCHES RELATING TO 



He points out that in the ovum before the first maturation division, the 

 nuclear chromatin breaks up into minute particles, described by authors 

 in some cases as too small for definition by the Microscope. Later, 

 these particles condense to form chromosomes ; but in view of the origin 

 of these, the author regards it as absurd to assume that they possess 

 such a form of bilateral symmetry as would render one form of division 

 quantitative and another qualitative. He not only rejects the current 

 distinction between qualitative and quantitative divisions, but doubts 

 the possibility of as yet including the maturation phenomena of different 

 auimals in one general statement. The attempt has, he believes, 

 already led many to do violence to the actual facts of observation. 



Spermatogenesis of Batrachoseps. * — Dr. Gustav Eisen finds that 

 the testis of this batrachian is admirably adapted for cytological 

 study, owing to the large size of the cells. As the result of his 

 observations, he gives the following account of the structures of the 

 cell. The eytosome consists of the cytoplasm, the plasmosphere, the 

 hyalosphere, the granosphere, the metaplasmic secretions, the cyto- 

 plasmic membrane of the various fibres and spindles, except the con- 

 tractile fibres. The nucleus or kari/osome contains the chromioles, the 

 chromomeres, the leaders, the chromosomes, the chromojdasm, the 

 endochromatic granules, the linin, the linoplasts, the nuclear membrane, 

 and the chrornoplast. The archosome consists of the centrioles, 

 the somosphere, and the centrosphere, centrioles and somosphere con- 

 stituting the centrosome of other authors. The spheres consist of 

 plasmosphere, granosphere, and hyalosphere, and are not permanent 

 cell-organs ; their three constituents have different functions. The 

 archosome usually lies within the granosphere. The chromioles are 

 the most minute visible elements of the chromosomes, are constant, and 

 are probably the bearers of the hereditary qualities. They are con- 

 nected together by chromoplasm, and are nourished by the endochromatic 

 granules. The chromoplasts are bodies having the staining reactions 

 of chromoplasm, which, by means of the linin, direct the movements of 

 the chromioles. The linoplasts nourish the linin network, and form 

 the true nucleoli. The archosome directs the formation of the spindle ; 

 its contained centrosphere is an organ of locomotion, by means of which 

 the archosome is capable of moving in the cell. The object of mitosis 

 is to produce the division of the chromioles, which, together with the 

 chromoplasts, the archosome, and the cell-wall, form the most permanent 

 structures of the cell. The other structures are for the most part 

 ephemeral, and have for their object the accomplishment of mitosis. In 

 the mitosis the author distinguishes two processes, the radiosonde and 

 the chromosomic. The first is controlled by the archosomes, and has 

 for its object the formation of spindles and fibres and the reconstitution 

 of the eytosome. The second is directed by the chromoplasts, and in- 

 cludes the formation and splitting of chromosomes, and the separation 

 of the halves. The two processes are parallel but independent. 



Differences in the Development of the same Ectodermic Struc- 

 tures, t — Dr. Karl Peter considers the development of the nerve-cord, 



* Journ. Morpbol., xvii. (1900) pp. 1-117 (14 pis.), 

 t Anat. Anzeig.. xix. (1901) pp. 177-98 (8 figs.). 



