156 A Summer Afternoon by the Sea. 



The alimentary canal appeared to nave a cloacal orifice,, 

 which, however, I did not distinctly define, between the fif- 

 teenth pair of fins (h), where I consider the tail to commence. 

 This portion of the animal is nearly of the same diameter 

 throughout, composed of nine segments, of which the bounding 

 furrows are distinguishable, notwithstanding what Grube says 

 to the contrary. The segments of the trunk, on the other hand, 

 are only to be inferred. Each segment-furrow bears a pair of 

 lateral processes. Of these, the earlier ones are not to be dis- 

 tinguished from the body-fins, which have been degenerating 

 from about the middle pair backwards, except by still further 

 degeneration; but as they approach the posterior extremity, 

 they become more and more rudimentary, and can scarcely be 

 discerned on the last one or two segments. The tail is perfo- 

 rated throughout by a viscus, which in most parts appeared 

 simple, though with corrugated walls, but near the base was 

 very manifestly composed of two cord-like portions, irregularly 

 twisted together — a strange and unaccountable structure. The 

 viscus inclosed at intervals two large oval air-bubbles, the effect 

 of which, though accidental and unimportant, on the appear- 

 ance of the animal, from the different refrangibility of the air, 

 was very striking. More structurally interesting was the evi- 

 dence of a circulatory fluid, surrounding and bathing both this 

 viscus in the tail and the alimentary canal in the trunk ; for at 

 intervals there were seen groups of blood-corpuscles whirled to 

 and fro and circling in irregular eddies, revealing the fact that 

 the body-cavity is lined with a ciliated membrane. This fluid 

 evidently bathed the whole interior of the body, and surrounded 

 the alimentary canal, without the slightest trace of a dorsal vessel. 



The walls of the body showed a texture composed of longi- 

 tudinal fibres, very distinct. 



Within the caudal cavity there was a series of organs of 

 whose nature I am doubtful. At the points where the degene- 

 rated fin-processes originate on each side, there was a gland(?) 

 shaped like a kidney-bean (i, and fig. 4), composed of pale 

 brown granular matter, attached to the inner wall by a short 

 stalk arising from the concavity, just as a bean is attached at 

 the hilum. The texture and appearance of these bodies had so 

 much resemblance to those of maturing ova (as in the Rotifera)^ 

 that I should have concluded such to have been their solution, 

 but for their isolated manner of attachment, and the absence of 

 any viscus that I could identify with an ovary.* 



* These glands are considered by MM. Carpenter and Claparede to be the 

 testes ; the form is probably inconstant, as they figure them of a very different 

 6hape. They found them filled with spermatozoa, which were furnished with two 

 whip-like tails- — " a common structure in the antherozoids of alga, but rare, if not 

 unique, among spermatozoa of animals." 



The ova in the female are lodged in the general cavity of the body and tail. 



