269 
was very conspicuous at the base of the passage (0), and by 
whose means it appears more than probable the evacuation 
of the spermatozoons is principally effected. 
After watching them to this condition of their existence 
the bodies grew gradually more languid in their movements, 
the caudal appendage ceased its vibrations, and sinking to 
the bottom of the receptacle containing them, the disintegra- 
tion of the whole rapidly set in. 
Unfortunately, the specimens set aside in a phial for 
future study have been mislaid, and the sketches made on 
the spot and a few brief notes constitute all the material 
left at my present disposal for drawing up this communica- 
tion. The day of their capture was an exceedingly busy one, 
and my non-apprehension at the moment of the many im- 
portant points still at issue in connection with their struc- 
ture and economy influenced me to bestow upon them a more 
cursory and superficial examination than I should otherwise 
have instituted. Hence the complex respiratory, circulatory, 
and neural systems, if present, escaped my notice; yet the 
evidence independently adduced is sufficient, I think, to 
justify the assumption that Appendicularia is neither an adult 
organism, as premised by Professor Huxley, Gegenbaur, and 
other writers, nor yet a true larval condition of some higher 
form, as supposed by Leuckart. The whole organism, in its 
matured state, as shown at fig. 2, being, indeed, a mere loco- 
motive reproductive sac, would lead me rather to suggest 
that we have here a true locomotive reproductive zooid, 
bearing, in all probability, a similar relationship to some sta- 
tionary tunicate! as the locomotive reproductive medusiform 
zooid does to the fixed Hydroid colony which gives it 
birth. 
Since my return to England I have carefully dissected 
numerous specimens of the large Ascidia mamillata; dredged 
in the same locality, in the hopes of finding some clue to the 
development of these puzzling organisms ; but hitherto these 
‘investigations have been unattended with success, though 
they have rewarded me in another direction by revealing an 
interesting example of “ commensalism,” the ample spaces 
between the folds of the tunic, in almost every instance, con- 
taining numerous specimens of an amphipodous crustacean 
closely allied to Leucothe, who had evidently made them- 
selves quite at home at those snug quarters. 
Before dismissing the subject, 1 must not forget to refer to 
the article on various species of Appendicularie and the 
1 Assuming from their likeness to the tailed larva of numerous Ascidia 
that they do belong to the same group. 
