HERMELLIDjE. 



separated from each other, from the hook-rows. Internally is a thick coating of sarco- 

 lemma, but only a few distinct muscular fibres. The ventral longitudinal muscles form 

 ovoid masses often pointed internally in transverse section, and have internally the sarco- 

 lemma and muscular fibres continued from the dorsal. A wide gap separates them in 

 the middle line. The nerve-cords are placed in the substance of each near the upper 

 and inner border. This position removes them from contact with both the circular coat 

 and the hypoderm, and also from the influence of the oblique muscles, which are well 

 developed, and in an example of 8, alveolata observed by Mr. Arnold Watson a slip 

 passed from one oblique muscle to the adjoining one. 



In the posterior region (Fig. 137) of a ripe male the muscular system is considerably 

 altered, for the entire coelom is occupied on each side by a great mass of sperms which 

 stretches from the lateral body-wall to the alimentary canal, and fills up the space between 

 the latter and the ventral wall. The atrophied dorsal longitudinal muscles form a thin 

 arch superiorly, each separated from its neighbour, and ending in a thicker lobe in the 

 midst of the sperms in the dorso-lateral region. The ventral longitudinal muscles are 



-vn-u 



Fig. 136. — Transverse section of the anterior region of Sabellaria spinulosa, Leuck. dm,, dorsal longitudinal 

 muscles; nc, nerve-cord; ph., pharynx ; vm., ventral longitudinal muscles; lu., muscular and other tissues 

 connected with the rows of hooks. 



also considerably attenuated, and form a somewhat clavate mass in section with the 

 narrow end innermost, but separated from the muscle of the opposite side by a long 

 interval. The nerve-trunks lie at the upper and inner border with a large neural canal 

 at the inner edge. The great thickness of the mucous coat of the alimentary canal is a 

 prominent feature, since atrophy of the gut is not unusual in other polychasts when the 

 reproductive elements distend the body-wall. The gut may have a respiratory function 

 in this case. 



In some species of Pallasia the neural canals are smaller in front than in the 

 posterior region, and this raises the question as to the physiology of these structures. 



Milne-Edwards 1 (1838) considered that in Sabellaria alveolata the centralisation of 

 the chief vascular trunks was less complete than in the Eunicidao, for instance, since there 

 are two main trunks only connected posteriorly, situated laterally, and an analogous 

 disjunction in the ventral vessel, which is single and median in the anterior fourth of the 

 body, and a part of the posterior, but presents two parallel trunks in the median region. 

 He corrects the view of Savigny that they were capitobranchiate annelids (the tentacles 

 being interpreted as branchiae). The figures illustrating the paper are excellent. 



1 f Ann. Sc. nat./ 2 e ser., t. x, p. 208, pi. xi, fig. 3. 



