382 r>R W. CARMICHAEL M'lNTOSH ON THE STRUCTURE OF THE 



Borlasia splendida, but he does not refer thereto in his descriptions. In the fresh 

 specimen it is found that the glandular papillae are much smaller than in Omma- 

 toplea, and widely different in shape (Plate VI. fig. 10, and Plate X. fig. 5), the 

 former representing them in the extruded proboscis, the latter as viewed from 

 without. Under ordinary circumstances they appear to have an ovoid shape, 

 and to vary from y-sVo^h to aooo th °f an mc ^ m s ^ ze - Under pressure they 

 become either flattened circular bodies or assume an elongated and slightly 

 barred aspect; and, after escape into the surrounding water, the contents are 

 club-shaped or rounded (Plate XIII. fig. 9). 



The usual crossing occurs at one of the poles of the circular section of the 

 proboscis in Linens longissimus (Plate XIV. fig. 8), but the separated piece at the 

 opposite pole is somewhat larger than in B. olivacea. Like the latter, it also has no 

 inner longitudinal fibres grouped exterior to the mucous layer. In the remarkable 

 form* dredged in 50 fathoms off Balta by Mr Jeffreys — and the structure of whose 

 body-wall coincided with the Meckelian type rather than the Borlasian — the 

 proboscis proceeded backwards from the tip of the snout in the usual manner, but 

 instead of the posterior end diminishing insensibly into the long muscular ribbon, 

 the organ divided into two nearly equal trunks (Plate XIV. fig. 12), each about as 

 large as the entire portion, and terminated in a somewhat abrupt and swollen 

 end, from which the long muscular ribbon proceeded. The wall of this peculiar 

 proboscis, so far as I could make out from the single and rather unfavourable 

 example, had the following structure: — Externally there was a circular layer 

 which showed a few granules on the outer margin in transverse section ; within 

 this lay a powerful and apparently continuous longitudinal muscular coat, from 

 whose inner surface the granular papillary mucous lining projected. The inner 

 or free margin of the latter was comparatively smooth, a result probably due 

 to the minuteness of the papillae. Each of the forked portions had the same struc- 

 ture as the anterior region, and the thick longitudinal coat, after bending inwards 

 at the posterior end of the swollen termination, became continuous with the 

 muscular ribbon. The proboscis thus differed from the ordinary Meckelian form 

 in the bifurcation, and in having no distinct circular coat within the longitudinal. 

 It had no closer analogy with the Borlasian or other type. 



In Micrura {Stylus), a true Borlasian, the organ is furnished with somewhat 

 slender papillae, which, under pressure, became lanceolate and pedicled, fusiform, 

 or rounded with granular contents. When viewed laterally, the rounded or 

 flattened papillae that formerly seemed granular appear to be composed of a series 

 of minute rods set closely together. In some of the elongated structures, how- 

 ever, under pressure, the striae are longitudinal. When extruded from the organ 

 into the water the elongated bodies in the papillae cling together in some instances 

 like fibrillae, and their appearance in the prepared specimens is quite charac- 



* Seep. 375. 



