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caudal point and the base of the foot. The whole internal surface of 

 the canal is probably lined with innumerable vibratory cilia, for, 

 though I have not observed them in this species, I have noticed them 

 commonly in the Rotifera. 



All the members of this class are considered to be hermaphrodite, 

 and the species before us is (exclusively, as far as I am aware) ovipa- 

 rous. The female organism is always conspicuous, consisting of an 

 enormous ovary, occupying the ventral region, commonly on one side. 

 Sometimes (as in A) it is a long, clear viscus, containing many trans- 

 parent globules, the rudimentary ova; and sometimes it is granu- 

 lated (as in B). Often a great developed egg may be seen (as in A) 

 occupying a large portion of the abdominal cavity; and sometimes a 

 second, also large, but less advanced to maturity. The eggs that I 

 have seen laid have been but few ; they measured about gloth of an 

 inch in length, and were covered entirely with short, flexible spines. 

 This was, however, in winter; at another season, they would pro- 

 bably be smooth. An animal which I isolated on the 19th of 

 February, with a large, nearly matured egg, deposited it on the 21st. 

 Voluntary motion of the foetus was perceptible in a day or two after- 

 wards, and from that time till the 1st of March, I saw every day, 

 through the transparent shell, the working of the body, the vibration 

 of the cilia, and an opaque, cloudy mass near the middle, probably 

 the ganglion. On that day, I lost it, eight days after laying, and 

 about a week after the first appearance of fcetal life. The eggs of 

 the Rotifera are ordinarily hatched in about twenty-four hours. 



Among the male organs may be reckoned, according to Prof. 

 Ehrenberg, that singular viscus, found in nearly all the Rotifera, and 

 in many of the Polygastrica, the contractile bladder. It occupies 

 the lower part of the abdomen, and when distended (as in B) takes 

 up a large space, displacing the surrounding viscera. It slowly fills, 

 and suddenly contracts into a wrinkled point, and these distensions 

 and discharges go on alternately ; but not at all times, for in many 

 specimens the organ cannot be seen at all. When distended, it 

 appears so clear that one might imagine a hole to have been cut 

 through the whole substance of the animal ; but on careful examina- 

 tion, numerous irregular vessels or muscular bands (?) are seen to 

 meander and ramify over its walls. 



A string of tortuous vessels, consisting of three at least, loosely 

 twisted together, run down the whole length of the body, on each 

 side (see H, 1). They commence near the head, and evidently termi- 

 nate in the contractile bladder (H, 2) at its posterior extremity. 



TRANS. MIC. SOC. VOL. III. O 



