INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 969 



Cordylophora, and Tuhularia) ; (b) both arise from the endoderm 

 {Eudendrium, Plnmidaria, and Sertularella) ; (c) the seminal arise 

 from ectodermal, and the ovarian products from endodermal cells. 

 It is interesting to note that no certain evidence is to hand of the 

 fourth possible combination — the male elements being developed 

 from the endoderm and the female from the ectoderm — ever having 

 been correctly observed. 



A further result of his observations is to be found in the fact that 

 in several Hydroids the ovarian cells chiefly arise in the ccenosarc of 

 the trunk, and only pass, during their growth, into the sexual knobs. 

 This is, further, to be confirmed by a reference to the statements of 

 Fraipont and of Van Beneden. The results of F. E. Schulze's 

 researches on Cordylophora would seem to be explicable by supposing 

 that he did not notice the very earliest stages, and that in Cordylo- 

 pho7-a the true scat of the origin of the cells is a portion of the 

 ccenosarc which belongs to the gonophoral region. 



Development of Hydra.*— Hcrr Kerschner has a preliminary 

 communication on the results he obtained, under the direction of Prof. 

 F. E. Schulze. There does not apjiear to be any morula-stage proper. 

 A blastula apjiears very early, and at its inferior pole, or that directed 

 towards the pareut, there is an invagination of cells, which go to 

 form the endoderm. There is not, as Kleinenberg imagined, any 

 conversion of the ectoderm into a chitinous investment for the embryo ; 

 but that layer does give rise to the connection between the mother and 

 the embryo. The endoderm cells increase by the development of 

 numerous protoplasmic connecting cords ; and the lacunje between 

 them have a counective-tissue-like appearance, which only becomes 

 altered by the closer approximation of the cells of this layer. The 

 oral pole of the young Hydra corresponds to the vegetative pole of 

 the ovum. 



Structure of Hydra. t — Herr Korotneff finds that the epithclio- 

 muscular cells of the " foot " are to be distingmshed from the other 

 ectodermal cells by their cylindrical form, their possession of a highly 

 refractive fibrilla, and the presence in their superior third of a 

 similarly refractive mucous secretion, by means of which the animal 

 is enabled to attach itself. These elements he would propose to dis- 

 tinguish as glandulo-muscular. At the beginning of autumn the 

 small, deei)ly-set cells o{ the ectoderm begin to jiroliferate actively, 

 and, arranging themselves in groups, they push their way between the 

 superjacent epithelio-muscular elements. These latter lose their 

 nuclei, and Lecome gradually absorbed. The cells thus lost are 

 replaced by a number of small cells, arranged in several layers. The 

 winter ectoderm cells, thus fi)rmed, undergo a fatty degeneration. 

 In consequence of the destruction of the muscular system, the animal 

 becomes considerably contracted, the endoderm gets folded, and the 

 cavity of the animal completely disappears. The develojunent of the 

 ova has many points of resemblance to that of the ectodermal cells just 

 described ; but it only occurs at certain points. Here the lowest lying 



♦ ' Z(«)l. Aiiz.eifi: ,' iii. (1880) p. 454. + Ibid., p. 10.".. 



