388 DR W. CARMICHAEL M'lNTOSH ON THE STRUCTURE OF THE 



so soft and delicate an organism bores through and tunnels the tissues of its host 

 is wonderful.* 



The Borlasiae readily feed upon fragments of mussel (as first noticed by Sir J 

 G. Dalyell). When a specimen has come in contact with a suitable portion, 

 the mouth is enormously dilated, and the bolus, even though of considerable size, 

 rapidly swallowed. The snout of the animal during this process is curved back- 

 wards, doubtless to afford assistance by its tactile properties, but there is no 

 extrusion of the proboscis. They also feed on dead specimens of Nereis pelagica, 

 ejecting the bristles and indigestible portions afterwards per anum. A specimen 

 measuring about three inches in length boldly seized the head of a large Nephthys, 

 upwards of four inches long, and partially ingulfed its prey. The danger of 

 putting rare specimens, such as Micrurce, together in a vessel is great, as the 

 larger generally makes a meal of the smaller. While thus predatory and vora- 

 cious, they are in turn tolerant of much injury ; for instance, one specimen had 

 its head and anterior portion seized and held in the stomach of a Sagartia troglo- 

 dytes for ten minutes, yet the worm subsequently got free, and crawled about as if 

 nothing had happened. After being put in spirit, they occasionally turn their 

 bodies inside out, and expose the inner surface of the digestive cavity. In Cepha- 

 lothrix the contents of the latter are easily observed, and often consist of frag- 

 ments of its fellows of the same species. 



Ehrenberg and de Quatrefages considered the mouth to be the genital 

 orifice, the former observing that a large quantity of mucus was discharged 

 therefrom. Mr H. Goodsirj thought the canal common to the respiratory, diges- 

 tive, and generative systems. " In Serpentaria" says he, " it acts almost as an 

 organ of digestion, while in Nemertes there is a trumpet- shaped exsertile pro- 

 boscis, which, contrary to the opinion of Rathke and other naturalists, and 

 according to the opinion already expressed by Ehrenberg, is the intestinal canal." 

 He agreed with Ehrenberg in supposing that the ova escaped into this chamber. 

 His views were rather erroneous, such as supposing that the first region of these 

 worms was composed of a single annulus ; but the succeeding or terminal of 

 many, each about an |th of an inch in length ; moreover, that each of the 

 separated annuli contained all the elements of the perfect or original animal, 

 viz., a male and female generative apparatus, the cavity common to the generative, 

 digestive, and respiratory functions, and a small dorsal vessel analogous to the 

 intestinal canal of Nemertes. Serpentaria, therefore, he explains, "is a com- 



* Since the foregoing was communicated to the Society, I find that Prof. Keferstein, in a 

 recent paper, gives a drawing of a parasite very similar to the above, but he does not say more about 

 it than simply mention, under the explanation of the plate, that it is an enigmatical body from the 

 stomach of a Leptoplana tremellaris. Beitrage zur Anat. u Entwicklungeschichte Seeplanarien von 

 St. Malo (Der K. G-esellsch. der Wissensch. vorgel. am 4. Januar 1868), p. 37, taf. ii. fig. 8. It is 

 probable that the same parasite, as in the case of the Gregarinae, may have a wide distribution. 



t Annals Nat. Hist. xv. 1845. 



