ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 265 



a depression, and where they become attached by their mesogloeal en- 

 velope and probably remain during their early developmental stages. 

 Great numbers of zooxauthellae inhabit the endoderm cells of the cceno- 

 sarc, gastric cavity, and tentacles lying in the bases of the cells next the 

 mesogloea. They are found in the process of division. They are not 

 so numerous in the ccenosarc, but in the large endoderm cells of the 

 tentacles they form a closely packed layer just within the peripheral 

 walls, thirty or more being found in a single cell. No nuclei of included 

 cells or pseudo-cells are found in the ova of E. griffini, and, inasmuch as 

 the zooxanthellaj show a marked resemblance in form and position to 

 the included nuclei or pseudo-cells figured by other authors, it seems 

 very probable that the spherical bodies found in hydroid ova and de- 

 scribed as included nuclei or pseudo-cells, were in reality zooxanthellse 

 taken in by the ova with absorbed endoderm cells. 



Abnormal Ephyra of Cyanea capillata.* — Joyce H. Robson de- 

 scribes a peculiar ephyra. Two of the eight arms had three lobes, with 

 two sense-organs between them. There were other irregularities in the 

 distribution of the sense-organs. The six normal arms had each one 

 sense-organ between the lobes, as is usual ; but one of them had also two 

 sense-organs close together, about halfway between the base and apex of 

 the arm, to one side of the middle line. The same thing was noticed in 

 one of the two abnormal (opposite) arms, while the other arm of this 

 pair had a single organ in the same position. The former arm had in 

 addition two sense-organs to one side of the third lobe instead of one, 

 making a total of five sense-organs for that arm, and three for the 

 other. 



Histology of the Medusae. f — Sophie Krasinska has investigated 

 the histological structure of the musculature and the peripheral nervous 

 system of Carmarina and Pelagia. In the peripheral nervous system of 

 both forms large and small ganglion-cells can be distinguished ; in 

 Pelagia only one kind of sense-cell occurs, while two kinds were found 

 in Carmarina. The large ganglion-cells of Pelagia are bi-polar, and are 

 often connected with the epithelial surface by a distal process. Those 

 of Garmarina are usually multipolar and sub-epithelial. The sub- 

 umbrella sense-cells differ considerably in the two forms. Those 

 of Carmarina are highly differentiated and suggest those of higher 

 Metazoa. In Pelagia the sense-cells, which bear short stiff bristles and 

 a long flagellum, are only recognizable by their nerve processes and their 

 connexion with ganglion-cells. The tentacles of Carmarina have sense- 

 cells, but none could be found in those of Pelagia. The most important 

 difference between the two forms lies in the distribution of nerve 

 elements in the sub umbrella and the tentacles. In Pelagia both large 

 and small ganglion-cells occur on the sub-umbrella and in the tentacles ; 

 in Carmarina the large cells are on the sub-umbrella, the small cells in 



* Eep. Dove Mar. Lab., ii. (1913) pp. 34-5 (2 pis.). 



t Zeitschr. wiss. Zool., cix. (1914) 1, pp. 254-348 (2 pis. and 5 figs.). 



June 17 th, 1914 T 



