194 CEREBRATTTLUS. 



the dilated termination is conspicuous on account of its reddish coloration. A groove generally 

 present on the side of the body is continuous with the end of the latter, but such a furrow, of 

 course, is only one of the variable longitudinal rugae of the body. The lips of the cephalic fissures 

 are usually kept in apposition, except at the posterior dilated portion. The mouth commences 

 just behind the ganglia, and forms a considerable longitudinal slit. 



On turning over a large stone in the litoral pool above mentioned a piece of the tenacious 

 grayish-white clayey mud so characteristic of the locality, and which was furnished with a smooth 

 groove, adhered to a corner on the under surface ; and on searching the now muddy pool from 

 which the stone had been raised, the rest of the firm clayey groove and a purplish or dark madder- 

 brown body about two inches long were found. The latter very much resembled the rough 

 siphons of a bivalve mollusk, being flattened, transversely rugose, somewhat abruptly truncated at 

 each extremity, hard and resilient under the touch. On placing this curious structure in pure 

 sea-water, the head of the animal was by-and-by pushed out from the dilated mass, not 

 by the gradual elongation of the whole, but as if an invisible power were drawing caouchouc 

 through a fixed aperture. It was transported to Scotland without difficulty, and lived there until 

 dissected, pushing its anterior end slowly about the bottom of the vessel, and seldom completely 

 extending itself. Indeed, the remarkable dilatation of the posterior end, which was often enve- 

 loped in mucus, was characteristic. Sometimes, however, the stretched tail was attached to mucus 

 at the bottom, while a dilated mass of the body remained about an inch in front of it, the rest of 

 the animal being attenuated, and perhaps laid along the water-line. Its habits on the whole 

 were sluggish, and corresponded with its native situation. 



On taking the animal out of the water after several months' confinement it contracted itself 

 firmly, an elliptical rent appeared on the ventral surface, and in a few seconds it ruptured into 

 four pieces. The anterior fragment with the head lived several months longer, and during 

 this time the posterior end had become considerably enlarged and paler, and there is no doubt the 

 original size and shape would have been gradually attained under favourable circumstances, while 

 its lost fragments were mounted as microscopic preparations. 



The skin gives an acid reaction to test-paper. 



An allied species was dredged by Mr. Jeffreys in the "Porcupine" Expedition, 1870, off 

 Cape Pinisterre, at a depth of 80 fathoms. 



Genus VII. — Cerebratultjs, 1 Benier, 1804. 



The species upon which this genus in the present work rests was probably known to 

 0. F. Miiller as Planaria angulata. Renier in 1804, in his e Prospetto della classe dei vermi,' 

 established the genus Cerebratulus for a worm which appears to have been allied to the present 

 form, and certainly one of the Anopla, if we may judge from Diesing's reprint of the characters 

 given by this author. I have chosen rather to run some risk in using Renier's name than to aid 

 in perpetuating the profuse nomenclature which arose chiefly from insufficient acquaintance with 

 the literature and anatomy of the subject. 



Generic character. — Body generally flattened, and thinned at the margins. Snout pointed 



1 Cerebrum, the brain ; probably from the fancied resemblance of the respective tissues. 



