ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 53 



cords wliicla Salensky, followiug Sommer and Landois, regarded as 

 water-vessels, are regarded as true nerves ; in longitudinal sections 

 their course can be easily followed ; the longitudinal nerves extend 

 through the whole of the body and unite at the posterior end. They 

 give off outwards at short distances small ramules, which jirobably 

 innervate the dermal musculature, and they also occasionally give off 

 internal branches. Some little way behind the anterior end of the 

 body the nerves give rise to a small thickening, which becomes united 

 by a commissure with its fellow of the opposite side. From the 

 thickened ends of this cerebral commissure a well-developed nerve 

 passes forwards, to supply the most anterior end of the body and the 

 muscular walls of the sucker. There is, on the whole, a not incon- 

 siderable resemblance to what obtains in the Trematoda. 



In conclusion, Dr. Lang sums up the state of our knowledge as to 

 the nervous system of the other Cestoda : T. perfoliata has a better 

 developed nervous system than the rest of the Tseniadse ; the anasto- 

 mosis or cerebrum contains nuclei and fibrils, gives off two lateral 

 primary trunks, and completely resembles in structure tlie same parts 

 in the Nemertinea ; T. solium, with others, has three cords on either 

 side. In the Bothriocephalida the water-vessels are on the outer 

 side of the longitudinal nerves, and here also the anastomosis is 

 concave anteriorly ; in the Ligulida the connecting commissure forms 

 a pretty broad bridge, the lateral trunks lie outside the water-vessels, 

 and are approximated towards one another in the anterior region of 

 the body. 



Development of the Ovum of Melicerta.* — L. Joliet points out 

 that the development of the embryo of Eotatoria has as yet been 

 studied in only two genera — Brachioniis by Salensky, and Pedalion by 

 Barrels. The mode of segmentation is still unknown. 



Although the author has ascertained | that the development of the 

 winter-egg and of the male egg agrees in a general manner with that 

 of the female summer-egg, it is more especially on this last that his 

 researches have been made. 



Within the maturation-sac it presents, in the middle of the 

 germinal vesicle, a small but very distinct germinal spot. After 

 deposition this spot speedily disappears. It did not appear to the 

 author that there was any emission of a polar globule. The first 

 segmentation-plane perpendicular to the major axis of the egg, which 

 is an irregular ovoid, divides it intcJ two very unequal segments. 

 Afterwards the two segments divide symmetrically, and so that each 

 furnishes eight of the spheres which constitute the egg in the stage 

 xvi. The spheres derived from the larger primary segment are larger 

 than the others, and also larger in proportion as they are further from 

 the animal pole. Each would appear to have, so to speak, a certain 

 degree of animality. Throughout the whole duration of the segmen- 

 tation, the part played by the nuclei and the asters is very remark- 

 able. A rotatory movement, already noted by Barrels in Pedalion, is 



* Comptes Kenclus, xciii. (1881) pp. 856-8. 

 t See this Journal, i. (1881) p. 894. 



