59 
IV. Further Researches on Tomopteris onisciformis, Eschscholtz. By William B 
Carpenter, M.J)., F.B.S., F.L.S., F.G.S., and Edouard Claparede, M.D. 
Fellow of the Physical Society of Geneva. 
Read January 19th, 1860. 
■ 
xxAVING been fortunate enough to capture a considerable number of specimens of this 
interesting Annelid during our joint sojourn at Lamlash Bay, Arran, during the month 
of September last, and having been able to add much to the knowledge previously ob- 
tained of its organization and reproduction, we have agreed to lay the results of our 
observations before the Linnean Society, in the form of a continuation of the memoir 
already communicated to it by one of us, and printed in its Transactions (vol. xxii. p. 353). 
Although we have much to add, we find nothing to correct in any of the positive state- 
ments of fact which that memoir contained ; and we have the satisfaction of bearing our 
joint testimony, based on a renewed comparison of Mr. George West's delineations with 
the objects from which they were taken, in regard to the truthfulness with which they 
represent the conformation of this interesting animal * . 
In the first place, with respect to the specific diversity affirmed by Drs. Leuckart and 
Pagenstecher f to exist between Tomopteris onisciformis and T. quadricomis, chiefly on the 
ground of the presence in the latter of a pair of cephalic appendages not possessed by the 
former, we have to state that the conviction already expressed by one of us % as to the 
insufficiency of this character has been fully borne out by our subsequent observations, 
which have entirely satisfied us that the presence or absenoe of the appendages in ques- 
tion depends solely upon the grade of development which the individual has attained. 
We have been led, however, by certain minute differences between the organization of 
the Tomopteris described by Leuckart and Pagenstecher, and that of the Tomopteris 
which we have studied, to suspect that the forms we have severally described under the 
designation T. onisciformis may not be specifically identical. 
The T. onisciformis and the T. quadricomis of Leuckart and Pagenstecher both possess 
that remarkable pair of "frontal horns," projecting laterally from the most anterior part 
of the head, which, as Mr. Huxley has remarked, give to the animal the aspect of a 
hammer-headed shark ; and they both possess that pair of greatly elongated appendages 
designated in the former memoir as the " styliform," but which we now prefer to term 
the second antenna. These organs are far longer, relatively as well as absolutely, in the 
In transferring these figures to copper, and in reducing their scale, the engraver has imparted to them a hard- 
ness and stiffness which the originals do not possess ; and has also, by too deeply shading them, destroyed the effect 
of transparency which the artist had aimed to give. 
+ Muller's Archiv, 1858, p. 588. - % See vol. xxii., supplemental note in p. 362. 
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