MUSEUM OF COMPARATIVE ZOOLOGY. 157 



the tube, but as narrow folds along the whole length of the vessel. The 

 stomach of a young Zygodactyla has a rectangular outline. Intermediate tubes 

 really begin to form while there are but four tentacles, while the figure re- 

 ferred to (N. Amer. Acal., Fig. 15G) has four chyniiferous tubes and ticenty-four 

 tentacles. 



The youngest Zygodactyla taken by me was captured with the drag-net in 

 the last of June. It was a little more than an eighth of an inch in diameter, 

 and is figured on Plate V. figs. 5, 6. The color of the bell on a black ground is 

 pale green ; that of the tentacles, cream-white. The radial tubes broad, four 

 in number, each one arising from an angle of the rectangular stomach, and ex- 

 tending the whole distance to the bell margin. There are also rudiments of 

 four other tubes, each of which arises from the side of the stomach midway 

 between the pairs of primary tubes, and extends half the radius of the bell, and 

 there ends abruptly in a slight enlargement. There are four tentacles corre- 

 sponding with the tubes which are fully developed, and beginnings of four 

 more, one midway between each pair of primary. The tentacles, as soon as 

 developed to any extent, are coiled up when the animal is at rest, just as is 

 the case in the tentacles of the adult. The outer surface of the bell is crossed 

 by four meridionally placed rows of lasso-cells. These diminish in size with 

 the growth of the Zygodactyla, and in the oldest medusae are almost com- 

 pletely lost. No tubercles exist on the under side of the umbrella of a Zygo- 

 dactyla as small as the example which I figure. Vertical outline of the 

 stomach rectangular. Development unknown. Although the ovaries were 

 crowded with eggs, I was imable to raise any of them, and cannot tell whether 

 it has a hydroid or not, except on the grounds of comparative embryology of 

 other and similar medusa). Variations in the course of the tubes, their union, 

 bifurcations, and number, are very numerous. In such cases of abnormal 

 growths the ovaries which accompany the tubes follow the same variations. 



Tima formosa A. Ag. 



Plate "VT. Figs. 1, 4, 5, 6. 



A Tima was very abuntlant at Newport, in May of the past year, which 

 later in the season disappeared altogether. In former years, I have begun my 

 work there in June, and have never had a specimen of Tima. These fixcts 

 lead to the conclusion that the medusa is a spring jelly-fish in Narragansett 

 Bay. 



Tivia formosa, A. Ag. is closely related to T. Bairdii of Forbes. Of the for- 

 mer species, the only representative of the genus on our coast, Mr. Agassiz 

 has given a good account. Lai"ger specimens, with more tentacles than he 

 mentions, were found, but in the main I have little to add to his description of 

 the adult. He says that the otocysts have from four to five otoliths. This 

 number is too small. In many otocysts of young jelly-fishes ten to fifteen 

 otoliths were counted by me. The otocysts often form new ones by a 



