154 A Summer Afternoon by the Sea. 



not be lost sight of, though still brilliantly transparent. And 

 in the course of the three or four hours occupied in my obser- 

 vations, it became less and less hyaline, increasing in opacity 

 as it decreased in size ; till at length, when I put it into spirit 

 for preservation, some five hours after capture, it was quite 

 opaquely white, and scarcely above half an inch in length. 



The body is slender, flattened, tapering to an attenuated 

 tail of great length ; much larger relatively in this individual 

 than in my Ilfracombe specimens, the tail occupying nearly 

 two-fifths of the entire length.* The lateral processes give an 

 appearance of flatness to the body, greater than it really pos- 

 sesses ; for when viewed sidewise, the trunk, independent of 

 the fins, is about as deep as it is broad. The body is furnished 

 with fifteen pairs of these lateral limbs (a a), which are mani- 

 festly analogous to the foot-processes in a Nereis or Syllis, but 

 show no traces of the pencils of bristles so characteristic of the 

 ordinary Annelida. Each foot divides at its tip into two thin 

 expansions of delicate sarcode (transparent fleshy tissue), each 

 of which assumes somewhat of a fan-shape, and is capable of 

 being convoluted into an obliquely truncate cone. I could 

 discern no appearance of external cilia. A transverse section 

 of the foot-base would have an elliptical outline, whose longest 

 diameter is vertical.f 



These terminal expansions are used as fins, being waved 

 in the water with great sprightliness and activity. They 

 thus constitute a powerful locomotive apparatus, and may be 

 instructively compared with the leaf-shaped swimming-fins 

 attached to the upper surface of the feet in Fhyllodoce. 



The head is remarkable for its accessory organs. J These 



* When this paper was written, I was not aware that the Tomopteris had 

 been the subject of two valuable memoirs by Drs. Carpenter and Claparede, pub- 

 lished in the Linnean Transactions for 1359 and 1860. Mr. Slack having 

 very kindly sent me an abstract of the latter, I add in notes some particulars 

 of structure wbich escaped my own observation. 



These eminent naturalists find that the animal passes through a larval stage, 

 which differs materially from the adult condition. They figure a larva, only '04 

 inch in length, in which the tail is altogether wanting ; there are but three pairs 

 of fins, the antennas, or first pair of head processes, are much larger than in later 

 life, and the cirri, or second pair, show only a commenced development. 



f Each of these processes, after the first five pairs, is furnished with two pairs 

 of minute rosette-shaped organs, one pair placed near the base of the fin, the 

 other on the terminal lobe-like expansions. The former are described as the ex- 

 ternal orifices of ciliated canals, which presently unite into one that runs along for 

 some distance in the wall of the body, and then terminates in the body-cavity. 

 These canals appear to admit the external sea-water to percolate into the cavity, 

 which is then replenished with the products of digestion by exudation through 

 the walls of the alimentary canal, and becomes a blood-like nutritive fluid. 



X MM. Carpenter and Claparede describe on the dorsal surface of the head 

 "a pair of ciliated epaulettes, uhich extend over the edges of the bilobed nervous 

 ganglion. These, at a certain stage of development, are fringed with long cilia, 

 both at their margin and at their base." 



