ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 161 



preserved eggs of Rhabditis nigrovenoea and Ascaris megalocephala. In 

 the first place he discusses the form of nucleus called mulberry-shaped 

 or polymorphic, and shows that the appearance of this shape may precede 

 either mitotic or amitotic division. In Ascaris megalocephala, again, 

 the nuclei of the first two blastomeres, as shown by Boveri, are unlike. 

 The author calls one of these blastomeres the primitive somatic-cell, and 

 the other the primitive sex-cell, from the structures to which they ulti- 

 mately give rise, and follows in detail the differences between their 

 respective nuclei and those of their respective daughter-cells. The 

 result is to show how important are these differences, for while the cells 

 which yield the future body contain in their nuclei numerous small, 

 rounded chromosomes, those of the cells yielding the future gonads, 

 retain the large horse-shoe-shaped chromosomes of the egg. In other 

 words, there is a diminution in the amount of chromatin in the somatic 

 cells as compared with the sex-cells. 



Germinal Vesicle of Reptiles.* — Marie Loyez describes some of the 

 changes in the nucleus of the ovarian ovum of Platydactylus muralis, 

 Lacerta muralis and viridis, and Anguis fragilis, and finds that while the 

 chromosomes change as to form, number, and staining reactions, they 

 never disappear. During the early changes, the nucleoli become more 

 and more conspicuous as the chromosomes become less dominant, but 

 there was no evidence of nucleoli being transformed into chromosomes, 

 or vice versa. Indeed, the staining reactions of chromosomes and nucleoli 

 remained distinct throughout. It is concluded that the nucleoli are in 

 some way essential to the activity of the germinal vesicle during the 

 period of vitellus-formation. 



Rheotactic Properties of Spermatozoa.! — F. Battelli, by means of 

 an ingenious little piece of apparatus, has experimented on the effect of 

 currents on spermatozoa. He employed for the experiment the sperms 

 of the guinea-pig in a nutritive solution, and with the spermatic fluid so 

 produced filled a glass tube with an internal diameter of £ mm. This 

 tube had ampullsB blown on it, and by heating the air in these the author 

 was enabled to produce currents of varying intensity in the fluid. He 

 found that active spermatozoa swim against and not with a current, 

 directing their heads in the direction opposite to that in which the 

 stream is moving. This is important, for it explains how they are able 

 to pass up the oviducts of the female in spite of the downward current 

 which the cilia of the latter must produce ; this downward current pro- 

 bably indeed promotes instead of hindering, as might be supposed, the 

 upward movement. 



Function of Sertoli's Cells.l — G-. Loisel has been led to conclude 

 that Sertoli's cells in the testes are derived from germinative cells, and 

 that their role is to secrete periodically a substance which exerts a posi- 

 tive chemotactic influence on the spermatozoa in process of development. 

 Through this influence the spermatozoa acquire the special form which 

 is so well adapted to their function. To this influence is due the dis- 

 position of the spermatozoa in bundles uniformly arranged. 



* Coaiptes Eendus, exxxiii. (1901) pp. 1025-6. 



f Arch. Sci. Phys. Nat. Geneve, xii. (1901) pp. 650-2. 



X Comptes Rendus, exxxiii. (1901) pp. 895-7. 



April 16th, 1902 m 



