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



with observers of unquestionable eomi^etency. And if, as would seem scarcely to admit 

 of doubt, the process of sexual generation is carried on in tlie portion which I imagined 

 to be larval, such a notion of its character becomes obviously untenable. I have deemed 

 it right, however, to record my first impression, that any observers to whom the animal 

 may present itself may have their attention more strongly dii'ccted to the peculiarities of 

 structure by which it was suggested. And as the animal does not seem to be very uncom- 

 mon on om' coasts (having been taken by the late Dr. Robert Bali in the Bay of Dublin, 

 and by Dr. S. J. Salter in Poole Harbour, as well as by Mr. Gosse and myself), it may be 

 hoped that fui'ther light may ere long be thrown upon this question, as well as upon the 

 nature and distribution of the nervous system of this beautiful and interesting creature. 



[Supplemental Note. — Subsequently to the reading of the foregoing paper, another 

 memoir on Tomopteris has been published in Midler's Archiv, 1858, p. 588, by Drs. 

 Leuckart and Pagenstecher. These observers describe, under the name of Tomopteris 

 onisciformis, a specimen with twelve pair's of fin feet and a caiidal prolongation destitute 

 of appendages, corresponding closely in its grade of development with a specimen I have 

 mentioned in p. 354. In the perivisceral cavity of the anterior part of its body, they 

 distinguished sexual products, as Busch and Huxley had done. They also describe, under 

 the name of Tomopteris quadricornis, a smaller specimen, having only ten pairs of fin feet, 

 and obviously identical with those first seen by me ; this they consider to be specifically 

 distinguished from the preceding by the presence of two pairs of horn-like appendages, 

 the T. onisciformis seeming to have but one. I have already mentioned, however, 

 that the second pair really exists in the larger specimens as in the smaller (p. 354) ; so 

 that there is no reason for regarding the two as otherwise than specifically identical, the 

 difference in the number of fin feet being obviously a character of age merely.] 



EXPLANATION OF THE PLATE. 

 Tab. LXII. 



Fig. 1. Young specimen of Tomopteris with ten pairs of fin feet; enlarged 10 diameters. 



Fig. 2. Head and anterior part of the body, as seen upon the dorsal aspect, enlarged 38 diameters ; 



a, bifid extremity of one of the fin feet. 

 Fig. 3. The same, as seen upon the ventral surface. 

 Fig. 4. Front view of the head, showing the position of the two anterior pairs of cephalic appendages, and 



the opening of the mouth upon the ventral surface. 

 Fig. 5. Caudal extremity, showing the last two pairs of least- developed fin feet, and the termination of 



the intestine in an anal orifice. 

 Fig. 6. Advanced specimen of Tomopteris with sixteen pairs of fin feet; enlarged 10 diameters. 

 Fig. 7. Posterior extremity of the body of the specimen represented in fig. 6, with its last four pairs of 



ordinary fin feet, giving origin to a caudal prolongation of very different conformation, furnished 



with eight pairs of rudimentary appendages. 

 Fig. 8. Specimen of Tomopteris with thirty-three pairs of appendages {Huxley). 

 Fig. 9. Masses of ova in the perivisceral cavity of the preceding [Huxley). 



