268 M. R. Louckart on the Young States of some Annelides. 



W\\\ch. certainly were greatly inferior in size to the corresponding 

 appendages of the middle of the body, and were further distin- 

 guished from these by the absence of bristles, and of the black 

 glandular pigment-spots, which, as is well known, are placed on 

 the segments beneath all the other pedal tubercles. The append- 

 ages of the two hindmost pairs were cleft, that is to say, they 

 each consisted of a dorsal and ventral cirrus, which however both 

 possessed the same cylindrical form. The foremost segmental 

 appendage on the contrary was perfectly simple, and appeared 

 in the form of a small, stumpy cirrus, which projected close 

 behind the eyes of the animal. The anterior part of the neck 

 bore a distinct range of cilia, running round behind the eyes and 

 mouth, which appears, from the observations of Krohn, to be 

 persistent on the ventral surface. The head had already acquired 

 exactly its future form and structure, but I could not succeed in 

 distinguishing the central frontal tentacle, which, however, is but 

 slightly marked even in the perfect animal. The globular eyes 

 project on either side but little beyond the neck ; it is well 

 known that in A, Raynaudii they by no means attain the same 

 colossal dimensions as in ^. Candida. Close to the mouth, and 

 underneath the eyes, a very considerable tubercle stands out 

 right and left, a kind of an upper lip, between the lobes of 

 which an elongated disc-like lower hp projects from behind. 



The caudal portion of the animal forms a narrow, stump-like 

 appendage, which at its root is scarcely half so broad as the 

 preceding terminal segment of the middle region of the body, 

 gradually tapers to its apex, and is about 1 line in length (rather 

 less than more). Microscopic examination shows that this tail 

 is annulated; a number of narrow segments may be distin- 

 guished in it, which gradually diminish in size and develop- 

 ment posteriorly. The foremost segments already possess the 

 future dorsal feet with their bristles and black glands; these 

 characteristics are gradually lost by the posterior ones, until 

 about the last fourth of the tail, which forms an undivided mass 

 with a rounded apex. I distinguished eleven distinct caudal 

 segments (with bristles), and behind these two or three other 

 indistinct (without bristles), which were just separated from the 

 apical piece. 



Regarding the internal structure I can say nothing that has 

 not already been mentioned by Krohn. The nervous system is 

 very distinct, at least as far as the middle of the tail, where it 

 gradually withdraws itself from observation in consequence of 

 the increasing opacity of the substance of the body. The anus 

 lies at the extreme apex of the tail, so that the intestine passes 

 through the entire length of the body. But it is only as far as 



