ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 15 



epithelium " of Clark, Eimer, and Klebs, the existence of which has been 

 so often denied, may be due to them. As to the function of the second 

 kind of bodies no suggestion is offered. 



Maturity of the Ovum.* — Dr. A. Carini discusses the problem of 

 maturity in the ovum. He refeis to the probable importance of £he 

 inquiry, as Thury has emphasized, in connection with the determination 

 of sex. In an historical resume he notes the various contributions which 

 from Barry onwards have been made to this subject. Barry referred to 

 the smaller mass of cellular droplets, Wharton Jones to the disappear- 

 ance of the germinal vesicle. Bischoff emphasized the increase in size, 

 the looser structure of ripe follicles, and the increase of liquor folliculi, 

 while Waldeyer called attention to the richer vascularity of ripe follicles, 

 the differentiation of layers in the granulosa, and the radiate striation 

 of the zona pellucida. His noted the increase of lymph spaces on the 

 wall of the follicle, Hensen emphasized the larger size, the oval form, 

 and the changes of the follicular cells. Von Baer had noted the peri- 

 pheral position of the nucleus. 



Carini has been impressed by the occurrence of eosinophilous elements 

 in the follicles of mature ova. In younger ova, both in nuclei and 

 protoplasm, the follicular cells have most attraction for hematoxylin, 

 while eosin staining only sparsely occurs in the protoplasm. He believes 

 that the susceptibility of eosin characteristic of the cells of ripe follicles 

 points to the progress of a degenerative process in these cells. 



Axis of Frog- Ovum.f — Dr. 0. Schultze responds at considerable 

 length to some strictures made by Boux upon his work on frog ova. 

 He reaffirms his old positions, and gives his reasons for doubting the 

 satisfactoriness of some of Roux's experiments. The axis of the ovum 

 corresponds in its course from dark to clear pole to the dorsoventral axis 

 of the embryo. The relation of this axis to the unfertilized egg is the 

 same as in all telolecithal vertebrate ova. From the moment of the 

 oblique posing of the egg after fertilization onwards, since the point 

 lying uppermost in the clear portion represents the position of the 

 blastopore and that of the future tail, the longitudinal axis is fixed ; it 

 passes from the point just mentioned at right angles to the transverse axis. 



Relation of Medullary Canal and Primitive Streak.}— Dr. J. 

 Kaczander has investigated the somewhat obscure point of the relations 

 between the primitive streak and the medullary canal. Chick embryos 

 were examined, beginning at the stage when the primitive streak is 

 visible to the naked eye, surrounded anteriorly by the dorsal folds. It 

 was seen that the residue of the streak — unused in the differentiation of 

 the body — includes the solid rudiment of the medullary canal. So far the 

 latter conforms to the rule in passing through a groove-like stage before 

 it is closed into a tube. Similar processes are seen in the bony fishes, 

 where, according to Schapringer, the central canal of the spinal cord 

 arises by a process of splitting within the solid rudiment, or, according 

 to Oellacher, by the divergence and partial dissolution of the innermost 

 cell-layer of the solid rudiment. There is this difference, however, that 

 in the Teleostei the groove-form never occurs, but the tube is formed 

 directly from the solid rod. 



* MT. Embryol. Inst. Wien, 1887, pp. 69-77. 

 t Biol. Centralbl., vii. (1887) pp. 577-88. 

 J MT. Embryol. Inst. Wien, 1887, pp. 26-32. 



