ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 29 



Reminiscence of Holoblastic Cleavage in Ovum of Cestracion.* — 

 Prof. Bashford Dean notes the interesting fact that in the eggs of Hetero- 

 dontus (Cestracion) japonicus, the surface which keeps uppermost, the 

 animal pole, is traversed by definite and sharply marked lines, separating 

 areas resembling the blastomeres in a late cleavage stage of Lepidosteus, 

 and easily visible from a distance of six or seven feet. The red-coloured 

 germinal disc is further down the side of the egg. 



The author presents the arguments for and against regarding the 

 lines as reminiscent of holoblastic cleavage, and concludes that there 

 can be little doubt that the lines are cleavage lines. We can thus con- 

 clude that the great size of the eggs of sharks was attained before total 

 cleavage became lost ; and that the yolk region of such eggs is homo- 

 logous with the lower pole-cells in other Ichthyopsids. 



Ophthalmic Nerves of Mustelus laevis.f— E. P. Allis, jun., has made 

 a useful analytic study of the ophthalmic nerves in this Selachian and in 

 other fishes. It is well known that there are in fishes several ophthalmic 

 nerves between which it is necessary to distinguish. While their exact 

 interhomologies cannot as yet be definitely affirmed, certain very probable 

 homologies can be arrived at, and there is no doubt that the problem 

 has been advanced towards solution by Mr. Allis's investigation. 



Development of Olfactory Organ of Ammocoetes4 — Dr. W. Lubosch 

 finds that the olfactory organ arises from an ectodermic thickening which 

 lies exactly in the position of the last connection between brain and 

 ectoderm. In Bdellostoma, according to Kupffer, the olfactory plate 

 appears ventrally to the neuropore, and the author suggests that the 

 difference is due to differences in the rate of development of the anterior 

 point of the head in the two types, in other words, to a difference in the 

 time of closure of the neuropore. Lubosch discusses the relation of his 

 observations to the comparison which Legros has elaborated between the 

 head in Amphioxus and in Ammocoetes. 



Relation of Metameric Segmentation in Petromyzon to that in 

 Amphioxus and in Higher Craniota.§ — Prof. S. Hatta directs attention 

 to the close resemblance between the history of the mesoblast in Petro- 

 myzon and in Amphioxus. In its earlier stages the differentiation of the 

 mesoblast in Petromyzon is exactly parallel with that in Amphioxus, 

 while in later stages it shows the features seen in the higher Craniota. 

 " We can thus observe in one and the same animal, Petromyzon, the 

 stages through which the primitive state of the mesoblast in Amphioxus 

 has developed into the condition in the higher Craniota." Thus the 

 lamprey is in this respect a connecting link. 



Influence on Offspring of Injecting Toxins into Parents. || — A. 

 Charrin and G. Delamare experimented with rabbits of both sexes, and 

 found that the injection of bacterial toxins was apt to be followed by 

 abortion, death at birth, nanism, rachitism, and various malformations. 

 Even digestive ferments were followed by abnormal results, and the 



* Annot. Zool. Jason., iv. (1901) pp. 35-41 (1 pi.). 



t Qnart. Journ. Micr. Sci., xlv. (19(11) pp. 87-236 (3 pis.). 



X Morph. Jabrb., xxix. (1901) pp. 402-14 (4 figs.). 



§ Annot. Zool. Jnpon., iv. (1901) pp. 43-7. 



II Comptes Rendus, cxxxiii. (1901) pp. 955-7. 



