ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 249 



of the " anterior " end of the intestine, internally to the lateral pro- 

 longations of the yolk mass. The male copulatory apparatus consists 

 of a vesicula seminalis and a ductus ejaculatorius. 



A paired canal with funnel-shaped internal opening, and appa- 

 rently opening externally, may be a segmental organ. No nervous 

 system, or water-vascular systems were observed. 



Reproduction and Development of Rotifer vulgaris.* — In the 

 waters from which 0. Zacharias found the specimens of Motifer vul- 

 garis that served as the basis of his studies, he found also PMlodina 

 roseola and Eosjyhora najas. The former rotifer was found under 

 two forms, one of which was very large (0 • 75 mm.) with a reddish 

 cuticle, and the other smaller (0 • 50 mm.) with a completely colourless 

 cuticle. 



The author refuses to recognize any similarity between the 

 external segmentation of the rotifer and the metamerism of the 

 arthropod ; the gastric glands have cells containing a pale granulated 

 mass, in which bright nuclei are deposited. By the aid of high 

 powers he has recognized that each " infundibulum " of the excretory 

 system has the form of a cylindrical cup, which is connected with the 

 excretory vessel by its narrower terminal piece. The cup is open 

 above, and the cilia project for a short distance beyond the orifice. 

 The author compares his results with those of Eckstein. 



The coelom of Botifer is characterized by being rarely quite free 

 of embryos ; as a rule three are found therein, one of which has 

 advanced some way in development, while the two others are only 

 just being formed. 



True cells were not detected in the blood, but the fine spindle- 

 shaped or rounded elements that are found in it have probably the 

 function of the blood-cells. 



The author describes the separation of the egg from the ovary, 

 which takes three or four hours ; the process is so effected that a part 

 of the investing membrane of the ovary is brought away with it, and 

 the embryo, during its development, lies in a hyaline circularly 

 closed vesicle, which may be regarded as a functional uterus. The 

 cleavage of the egg is very difficult to observe, on account of the 

 movements of the animal, and of the contractions which result from 

 the slightest pressure. By the exercise of patience during six months, 

 Zacharias was able to convince himself that the egg when separated 

 from the ovary has a central germinal vesicle and spot ; the contours 

 of the vesicle become indefinite, and at last it is invisible. The yolk- 

 granules now show a tendency to collect into the middle of the egg, so 

 that a dark central mass may be distinguished from a lighter peripheral 

 portion. When, as soon happens, the contents clear up again, it may 

 be seen that there has been a division of the germinal vesicle ; the 

 mode of division appears to have some relation to gemmation. There 

 is an interval of some hours between the division of the vesicle and 

 the formation of blastomeres. 



The rudiments of the mesoderm were seen to arise by cleavage 



* Zeitschr. f. Wiss. ZooL, xli. (1884) pp. 226-51 (1 pL). 



