538 SUMMARY OF CURRENT RESEARCHES RELATING TO 



show nucleated blastomeres and cytoblastomeres. In the areas of full 

 activity there are normal or abnormal karyokineses, cytasters, and 

 divisions of cytasters. Apart from the absence of denned centrosomes 

 in the aster?, and the origin and number of the chromosome 15 , the 

 essential phenomena agree with those descriled by Wilson in the un- 

 fertilised ova of Toxopneustes. 



Disruptive Processes in Ovarian Ova of Lacerta agilis. * — J. A. 

 Meyer finds that appearances suggestive of cleavage are really disrup- 

 tive. Tbe plasmic masses are irregular ; they are without nuclei ; the 

 germinal vesicle disappears ; the yolk becomes fluid ; leucocytes wander 

 into the egg ; the follicular epithelium first proliferates and then breaks 

 up. 



; Internal Secretion of Testis.f— G. Loisel has studied the testes of 

 birds and mammals in embryonic and adult life, and distinguishes what 

 he calls a primary, chemical, internal secietion from the secondary, 

 morphological, external secretion (that of spermatogenesis). In its 

 internal secretion the testis is a great destructor of fat ; hence the 

 frequently greater thinness of males, their emaciation during the 

 breeding period, and the fattening of castrated individuals. 



Spermatogenesis in Newt.'j — J. A. Janssens describes the various 

 stages, and emphasises some new points. Of especial importance is the 

 comparison between the phenomena of spermatogenesis and those of 

 oogenesis, and the theory that the successive " resolutions " of the 

 nucleoli in the ova may correspond to the successive divisions of 

 the spermatogonia. The author also makes a point of insisting on the 

 intimate relations between the chemical processes of metabolism and 

 nutrition on the one hand, and the physical processes of cell-division 

 on the other. 



Spermatozoon of Rat.§ — A. A. Merlin has made a detailed examina- 

 tion of a fine preparation of rat spermatozoa, and describes the appa- 

 rently somewhat complex minute organisation of the " head.'' 



Two-tailed Spermatozoa. || — E. Ballowitz refers to Bromann's recent 

 description of two-tailed spermatozoa in the normal spermatic fluid of 

 man, salamander, and dog-tisb, but recalls his own paper of 1891, in 

 which the occurrence of similar forms was carefully noted. 



Alleged Peritubular Lymphatic Tubes of the Testis.f — M. A. 

 Capurro believes that the free peritubular spaces seen on section of the 

 testes and often described, are really artefacts, due to the effect of the 

 mode of preparation on the glandular material. 



Development of Layers of Retina.** — J. Cameron notes that the 

 inner wall of the retinal cup in a fourth-day chick has exactly the same 

 structure as the wall of the embryonic cerebral vesicles or spinal cord 



* Anat. Hefte (Merkel and Bonnet), 1901. pp. 71-96 (4 pis.). See Zool. Cen- 

 tralbl., ix. (1902) p. 153. 



t Comptes Rendus. exxxv. (1902) pp. 250-2. 

 X Anat. Anzeig., xxi. (1902) pp. 129-38 (15 figs.). 

 § Journ. Quekett Micr. Club, viii. (1902) pp. 189-94 (2 figs.). 

 || Anat. Anzeig., xx. (1902) pp. 561-3. f Tom. cit., pp. 563-9 (4 figs). 



*• Proc. Roy. Soc. London, Ixx. (1902) pp. 84-6. 



