1882.] 
441 
[Kingsley. 
SOME POINTS IN THE DEVELOPMENT OF MOLGULA 
MANHATTENSIS. 
BY J. S. KINGSLEY. 
The following notes on the development of Molgula manhat- 
tensis are the results of observations made in the Slimmer Labora- 
tory of the Boston Society of Natural History, at Annisquam, 
Mass., during the months of June and July, 1881 ; and while they 
have not that completeness which could be desired, they may add 
something to our knowledge of the embryology of the interesting 
group of Ascidians. 
The earlier stages before the formation of the tail were obtained 
by cutting open the parent and taking out the yellow eggs and 
embryos, the later by rearing the larvae in confinement. The 
larvae and young Ascidians are very tenacious of life and will live 
for weeks in a dish without any change of water, but care should 
be taken to keep out all dust, as otherwise the young ascidian, 
after becoming attached, will cover itself with foreign matter 
thus rendering it difficult to obtain satisfactory views of the 
internal structure. Owing to the minute size of the embryos 
(less than } mm. in diameter) section cutting was out of the 
question, while the opacity of the young until some little time 
after it became attached prevented any observations upon the 
internal structure, except those made on the tail of the “ tadjDole.” 
All methods of clearing employed by microscopists, known to the 
writer, were tried, but they only resulted in a great distortion of 
the specimens which nevertheless remained as opaque as before. 
All figures are from camera drawings. 
The ovarian egg (pi. 9, fig. 1) is small and presents no especially 
important features. The nucleus and nucleolus are usually well 
marked. Occasionally an egg was found (fig. 2) in which the 
nucleus contained several strongly refractive bodies. The next 
observed stage was the mature egg (fig. 3). Here the egg has 
increased in size, become more opaque by the production of yolk 
granules, and the nucleus and nucleolus have become much less 
distinct. A new feature has also appeared : Around the egg- 
proper a second membrane has been developed and between this 
and the yolk are found numerous “ test cells.” Regarding these 
