ZOOLOGY AND BOTANY. MICKOSCOPY, ETC. 299 



have 23 chromosomes and some 24, and it seems that there are 47 

 chromosomes in the somatic cells of man and 48 in those of woman. 

 The heterochromosome is regarded as a " sex-chromosome." 



Heterochromosome in Human Spermatocytes.* — S. Gutherz finds 

 in the spermocytes of man, besides 1-3 true nucleoli, a basophil nucleolus 

 which may perhaps be regarded as a heterochromosome. This is sug- 

 gested by its staining reactions, by its minute structure (double rods or 

 tetrad), and perhaps by certain changes of shape. As there is no 

 demonstrable heterokinesis nor dimorphism of spermatid nuclei, the pre- 

 sumable heterochromosome may be regarded as a pair of equal chromo- 

 somes. Guyer's description of a sex-chromosome in man is not confirmed 

 by Gutherz. 



Spermatozoa Penetrating into Blastulae.t — J. H. P. Kohlbrugge 

 finds evidence in the rabbit that spermatoza pass through the zona and 

 lie between it and the segmented ovum, and that they may even enter 

 the blastomeres. In the bat he previously found evidence that sperma- 

 tozoa may penetrate into the blastula, and that happens in the rabbit 

 also. 



Alleged Dental Primordia in Birds. J — Hide has studied the 

 embryos of a parrot {Ifelopsittacus undidatus) and finds no evidence of 

 the alleged dental primordia. The " tooth-papillae " of Geoffrey St. 

 Hilaire are sharp hard papillse, analogous with teeth, but not homologous 

 with them. There is no hint of dentine nor of a dental ridge. Similarly 

 the " dental system " alleged by Blanchard, and the " teeth " alleged by 

 Fraisse cannot be accepted. They have no relation to true dental pri- 

 mordia. Furthermore the " dental ridges " of Rose are not true dental 

 ridges : they are connected with the development of the horny bill. 



Development of New reathers.§ — Frieda Bornstein has studied 

 young ducks, pigeons, swifts, etc. A new germ is always formed for a 

 new feather ; the new germ arises while the old feather is still growing ; 

 it is formed from the malpighian layer, at one side of the base of the 

 feather follicle. The new feather-germ forms a process which grows 

 into the deeper layers of the cutis, and from this process the new papilla 

 is formed. The old papilla atrophies after the old feather falls off. A 

 study of the foot of the capercaillie, where feathers and scales occur in 

 close association, led to the conclusion that a feather corresponds not to 

 an entire scale but only to part of a scale, the rest being suppressed. 

 This corroborates the work of Ghigi. 



Early Stages in Development of the Gonads in Axolotl.|| — 

 G. Spehl and J. Polus find tliat the first indisputable primordia are 

 situated in the dorsal portion of the lateral plates of the embryos. 

 They are paired and symmetrical, and purely mesoblastic. At all stages 

 they lie internal to the Wolffian canals, and they remain for a long time 

 in continuity with the lateral plates, of which they form the dorsal 



* Arch. Mikr. Anat., 2te Abt. Ixxix. (1912) pp. 79-95 (1 pi. and 2 figs.). 



t Arch. Mikr. Anat., Ixxvii. (1911) pp. 82-5(2 figs.). 



t Arch. Mikr. Anat., Ixxix, (1912) pp. 2-47-75 (3 figs.). 



§ Arch. Naturges., Ixxvii. (1911) pp. 1-11 (2 pis.). 



II Arch. Biol., xxvii. (1912) pp. 63-90 (2 pis. and 3 figs.). 



Y 2 



