ZOOLOaY AND BOTANY^ MICROSCOPY, fiTO. 553 



matic elements sometimes happens at a time when there is no indieation 

 of the achromatic figures of division. The most striking of these cases 

 has been lately described by Flemming. Similar phenomena have been 

 observed by the author in the eggs of Ascaris. In the germinal vesicle 

 of A. lumhricoides the twenty-four rods exhibit the most distinct transverse 

 division, long before the germinal vesicle begins to be converted into the 

 spindle. 



After considering several cases in different forms the author expresses 

 his belief that they form parts of a series in the degeneration of the 

 process of nuclear and celliilar division. In the case of Gorydalis cava, 

 described by Strasburger, the process is least rudimentary ; two typical 

 daughter nuclei arise, but these again fuse into a single nucleus; in 

 Thysanozoon and A. megalocephala daughter stars or plates are formed, 

 but at once pass into a single resting nucleus. In the cells of Flemming 

 and Carney there is a division of the chromatic elements, but no 

 arrangement in two groups. 



Herr Boveri suggests that in the parthenogenetic eggs described by 

 Weismann as having only one directive corpuscle we have to do with 

 the same process as in the eggs of Ascarids ; there are two divisions, 

 but the second is limited to division of the chromatic elements. If this 

 be so, the parthenogenetic development is not to be regarded as dependent 

 on the suppression of the development of the second directive corpuscle, 

 but by its retention in the egg, and the fusion of its nucleus with the 

 ovarian nucleus. The second directive corpuscle may then be regarded 

 as playing the part of the spermatozoon, and it may be said that 

 parthenogenesis is due to fertilization by the second directive cor- 

 puscle. 



In the achromatic nuclear figure the mode of origin of the spindle, 

 and the complete want of polar rays are of significance. The often dis- 

 cussed question whether the nuclear spindle is derived from the substance 

 of the nucleus or of the cell may, in the case of Carney's type of A. 

 megalocepliala, be certainly decided in favour of the former. 



A number of points in Carney's account of the phenomena of matura- 

 tion of the ova of Nematodes are discussed, and corrections offered. 



Flemming on the Cell.* — Prof. N. Flemming has been investigating 

 the cellular division in the spermatocytes of Salamandra maculosa. He 

 finds that these cells exhibit a remarkable dimorphism of mitosis ; in 

 the heterotypical form the chromatic formations exhibit metakinesis. 

 The two forms, the other of which may be called homoeotypical, are 

 sometimes found together, but, as a rule, the heterotypical form is found 

 in the first multiplication of the testicular epithelium after fecundation 

 (April or May). In both types the chromatic filaments undergo a 

 longitudinal division. All the differences, it should be remarked, pre- 

 sented by mitosis, whether in spermatocytes or other kinds of cells, are 

 simple peculiarities of form and aspect, and are in no way fundamental. 

 In the heterotypical form the extremities of one pair of divided filaments 

 unite in the same way as in the egg of Ascaris megalocephala ; the united 

 parts are, later on, placed at the equator, and when they become 

 definitely separated, one might believe that the separation of the loops 

 was effected transversely, whereas it is due to longitudinal division. 



* Abstract ia Arch. Zool. Exper. et Gen., v. (1887) pp. xxxiii.-v. Original 

 source not cited. 



