ZOOLOGIY AND BOTANY, MICROSCOPY, ETC. 253 



In the last part the Hydromedusinse, Hydrocorallinfe, and Traehy- 

 medusso are dealt with, and the paper concludes with a table of 

 all the known Australian species. The total number of species is 

 231 (69 genera). The most interesting of the thirty new species are 

 illustrated. 



Development of Lucernaria.* — N. Kowalevsky finds that the 

 fertilized ovum divides in the usual manner till thirty-two blasto- 

 meres are formed, forming a compact unilaminar morula without a 

 segmentation-cavity. The appearance of the entoderm took place 

 about fifteen hours after the ovum was laid. A single, central, ento- 

 dermal cell was observed, which may have originated from the central 

 ends of the cells of one side of the morula, but possibly by one of the 

 original cells withdrawing to the interior. Prof. Kowalevsky in- 

 clines to the former view, but states that he has seen the entoderm 

 cell with a delicate prolongation extending between the outer cells to 

 the periphery. Multiplication of entoderm cells leads to the pre- 

 viously spherical embryo becoming elongated, the larva assuming 

 the form and structure of a simple hydroid tentacle. In this state 

 the (unciliated) larva creeps about after the manner of a hydra. 

 Towards the third day the formation of nematocysts in the ectoderm 

 begins as small vesicles, and is completed by the end of the third day. 

 On the fourth day the larvae fixed themselves, and again became 

 round, though somewhat flattened, bodies. The hitherto uniserial 

 entoderm lost its linear character, and formed an entodermic mass 

 sharply marked ofi" from the ectoderm. It was not possible to decide 

 positively whether at this stage there was an entodermic cavity. Soon 

 after fixing themselves a cartilaginous cyst was secreted, and within 

 this the larv83 existed about a fortnight, and then from time to time 

 escaped, and could not be further studied. 



Structure of Sarcodictyon.t — W. A. Herdman describes very 

 fully the anatomy and histology of specimens of Sarcodictyon catenata 

 Forbes, from Lamlash Bay, Arran, and from Loch Fyne. Eed and 

 yellow varieties were found at the latter locality. He considers that 

 Forbes' S. agglomerata and Pom-tales' S. rugosum are possibly the 

 same as S, catenata, in which case there is only one well-marked 

 species of Sarcodictyon known to science. 



Porifera. 



Nervous System of Sponges. J —E. v. Lendenfeld describes the pre- 

 sence of nervous elements and ganglion-cells in the Heterocoela (Pole- 

 jaeff) ; such appear to be absent in the Homocoela. In the Sycones 

 the walls of the pores contain groups of spindle-shaped cells, meso- 

 dermal in origin, which are frequently connected with branched cells, 

 apparently of a ganglionic nature. In the Leucones sensory cells are 

 present, but not concentrated round the pores ; they are scattered 



* Zool. Anzeig., vii. (1884) pp. 712-7. 



t Proc. R. Phys. Soc. Edinburgh, viii. (1884) pp. 31-51 (3 pis.). 



X Zool. Anzeig., viii. (1885) pp. 47-50 (2 figs.). 



