DR. W. B. CARPENTER ON TOMOPTERIS ONISCIFORMIS. 359 



plain tube as far as the first fourteen or fifteen pairs of appendages. It then becomes 

 transversely folded and wrinkled, and thus passes, preserving a very even diameter, to 

 the end of the body. 



" The cavity of the body contains, floating about between the intestine and the parietes, 

 certain rounded free masses. These are made up of other more or less rounded masses, 

 flattened when their sides are applied to one another (fig. 9), which have perfectly the 

 structure of ova. These ova had a diameter of a-hjth of an inch, and less. In those of 

 the former size the germinal vesicle measured s^th of an inch, and was clear and delicate. 

 The germinal spot, vesicular and thick-walled, measured ygVoth of an inch. 



" The appendages are hollow processes of the body, and their cavities are continuous 

 with that of the body, as was evident from the passage of the ova from the one into the 

 other. They increased in size to the fourth or fifth pair, and diminished again from the 

 seventh or eighth. The first sixteen or seventeen pairs consisted of a stout basal portion 

 terminated by two divisions, each of which was provided with a flat, vertical oar-like 

 expansion. The remaining appendages became smaller and smaller and more rudi- 

 mentary. The anterior ones were provided with two conical processes merely, while the 

 posterior ones were themselves nothing but short simple processes. There was a short 

 space between the last pair of processes, which were mere buds, and the truncated anal 

 extremity. 



" At the re-entering angle between the second pair of cephalic appendages and the 

 narrow neck, there is, on each side, a rounded elevation, from which a sort of band or 

 ridge runs back upon the dorsal surface. 



" On the ventral surface, close to the two rounded elevations, a long, curved, spine-like 

 process arises upon each side. In their natural position these two processes lie parallel 

 with one another, one on each side of the mouth. 



" Aug. 28th. — A small specimen obtained to-day appears to be a male, for it contained 

 masses of round cells, each rather more than g-j^th of an inch in diameter, in the place 

 of the masses of ova of the previous specimen ; these were perhaps young spermatozoa. 

 In other particiilars its structure agreed with the foregoing." 



It is obvious that Professor Huxley's specimen must have been in a more advanced 

 stage of development than mine, since it had no fewer than thirty-tliree pairs of append- 

 ages, and was also maturing its sexual organs. His figure and description indicate that 

 the conformation both of the body and extremities underwent a change at about the six- 

 teenth or seventeenth pair ; but the transition seems to have been far less abrupt than it 

 was in my specimen ; so that he does not appear to have been struck with any very 

 decided difference in the conformation of the anterior and posterior parts of the body. 

 And his figure of one of the appendages of the latter would seem to indicate that in then- 

 more advanced condition these approach more nearly to the type of those of the anterior, 

 than they seemed to me likely to do. 



Tomopteris onisciformis was first described by Eschscholtz, who briefly characterized and 

 rudely delineated it in the ' Isis ' for 1825 (p. 735, pi. 5. fig. 5), assigning to it a place 



