

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



large, a parois tres-contractiles, qui parait et disparait par intervalles, occupe la 

 ligne mediane et semble s'ouvrir au bout de la queue." A reference to his 

 figure* and its explanation at once makes it apparent that he has mistaken the 

 proboscidian sheath for a blood-vessel. Prof. Keferstetn again does not enter into 

 detail with regard to the circulation in Borlasia, and his figures and descriptions 

 apply to Ommatoplea, with two exceptions,! which represent transverse sections 

 of Cerebratulus marginatus. In that through the anterior part of the body five 

 circular vessels at least are transversely cut in the meshes round the oesophageal 

 region, and, moreover, they are connected together by a pink band in the figure, 

 as if from a connecting trunk. I fear the author has been misled by the carmine 

 used in the preparation, for in the British examples of Cerebratulus a true 

 Borlasian arrangement is found. 



Generation and Development. — The sexes are separate, as in Ommatoplea, 

 and the ova and spermatozoa developed in their respective sacs between the 

 inner muscular layer of the body and the digestive cavity. The glandular ele- 

 ments in the walls of the latter indeed undergo a certain amount of atrophy 

 during the period of reproductive perfection, as observed in the transverse 

 section through a specimen just before spawning (Plate XII. fig. 3). 



In Borlasia olivacea the spermatozoa (Plate X. fig. 9) have the aspect of slender 

 rods, with a scarcely perceptible enlargement at the end from which the filiform tail 

 proceeds. When a mass is taken from a living animal, they often adhere to a point 

 by one end, and, spreading around this in a radiating manner, lash the surrounding 

 water with their tails. The spermatozoa of B. octoculata (Plate XI. fig. 5) are more 

 minute than the former, and somewhat resemble an awl-handle in shape, with 

 the filament projecting from the butt, which is thus frequently agitated, while 

 the tapered end is comparatively still. In Linens longissimus the outline of the 

 body of the spermatozoon (Plate XI. fig. 4) is less regular than in Borlasia, and 

 it seems slightly crenated or moniliform. A very long filament proceeds from 

 the body at the larger end. In Micrura fasciolata there is likewise a slight 

 constriction in the middle of the spermatozoon, and the tail proceeds from the 

 larger extremity. 



The ova are few and large in B. olivacea, smaller and more numerous in 

 B. octoculata. Both ova and spermatozoa escape by pores on each side a little 

 above the nerve-trunks, these apertures being often indicated by pale specks 

 along the sides of the worm, and occasionally, as in Meckelia annulata, they 

 are boldly marked by white spots. In this species also the rudimentary condi- 

 tion of the generative organs may be seen in transverse section as a series of 

 small globular or pyriform sacs, filled with granules and globules, and situated 

 above the lateral vessel on each side of the body. Thus far there is a certain 



* Op. cit. pi. iii. fig. 4. f Zeitscli. i. w. Zool. xii taf. vii. figs. 3 and 4. 



