THE HISTORY OF BALANOGLOSSUS 



431 



his two, B. clavigerus, Dell. Ch., and B. minutus, Kow. I shall hereafter n»tk of 



our species as Balanoglossus Kowalevskii. The New England Balanosrlossus is 



.~„« ^.uuuug 



found at low-water mark, buried in the sand (only in the cleanest sand-beaches) to 

 a depth of about twelve or fourteen inches. It is readily tracked on the surface by 

 the peculiar elliptical coils of sand which are thrown out at the top of the hole. The 

 hole in which they live is lined by a thick mucous layer, forming a sort of sheath 

 of considerable diameter, in which the worm must evidently be able to move up ami 

 down with considerable ease. Owing to the extreme tenuity of the walls of the 

 posterior part of the body, and its great length in adult specimens, it is quite dim- 

 cult to obtain complete full-grown specimens; but of the smaller sizes, where the 

 posterior part of the body behind the gills has not yet taken a great development, 

 it is quite easy to obtain whole specimens. 



The proboscis is elongate, slightly pyriform, somewhat flattened, rounded, or pointed 

 at the anterior extremity ; it is of a pinkish-yellow color. The proboscis is attached to 

 the upper part (dorsal) of the collar ; it is rounded posteriorly, slightly indented on 

 the median dorsal line. Seen in profile, its base of attachment is found to be quite 

 slender ; the body of the proboscis is bevelled anteriorly ; the space between the lower 

 part of the proboscis and the cavity of the collar is occupied on the base of the 

 proboscis by the avenue leading to the mouth, a large elliptical opening capable of 

 little expansion or contraction. The whole proboscis is occupied by a cavity open- 

 ing anteriorly by a small orifice ; a second opening, subsequently formed, is placed 

 on the lower surface of the proboscis immediately in front of the mouth. The 

 proboscis, as has already been stated by Kowalevsky, is the main organ of locomotion : 

 water and sand are taken in at one extremity and forced out at the other, the animal 

 moving the rest of the body by drawing it after the proboscis, which thus acts as a 

 kind of sucker. The capacity for motion of the body situated behind the collar 

 is limited to simply twisting and gliding, while the moving force is applied by the 

 proboscis and collar. The proboscis is extremely variable in outline ; it is capable 

 of great expansion and contraction, the whole proboscis being lined with longitudinal 

 and transverse muscles, which make their appearance in the earliest stages of the 

 young Balanoglossus ; the longitudinal muscles are by far the most numerous ; con- 

 centric muscles are found round the two openings of the proboscis. The cavity of 

 the proboscis has no connection whatever with the cavity of the body into which the 

 mouth opens, as has been correctly maintained by Kowalevsky, in opposition to 

 the statements of Delle Chiaje and Keferstein. On the dorsal side, at the base 

 of the proboscis, is situated the skeleton of which I have spoken above, which 



