Gatty Marine Laboratory, St. Andrews. 33 



Eugen Leo* (1912) describes the blood-vessels and 

 sinuses in Protula, Vermilia, and otfter Serpulids : — The 

 main channels, he states, are determined by the mcta- 

 merization and differentiation of mesodermic bands which 

 arise from pole-cells. The gaps between the splanchno- 

 pleure and intestinal epithelium, or between the neural and 

 haemal mesenteries and septa, give rise to channels for the 

 nutrient fluid diffusing through the epithelium of the gut. 

 The channels at first have no proper walls. The walls of 

 the visceral sinus and dorsal and ventral vessels are due to 

 m uscular differentiation of the splanchnopleui e The lumen 

 of other blood-channels is interseptal and closed off by 

 peritoneal walls from the ccelom. 



As indicated in the remarks on Bispira, E. Meyer has 

 devoted much attention to the structure of the Serpulids, 

 which he contrasted chiefly with the Hermellidse. He also 

 followed the development of the thoracic nephridia in 

 Psygmpbranchus protensus, and went minutely into the 

 processes and collar of the anterior region. His observations 

 on the various organs, though somewhat diffuse, are of much 

 interest. The Sabellids were included with the Eriographi- 

 didse and Serpulidae under his Serpulidse. 



A prominent feature hi the anterior body-wall of Protula 

 tubularia-, Mont., is the great size of the dorsal longitu- 

 dinal muscles, thus agreeing with Pomatocerus. The cuticle 

 and hypoderm are well developed throughout, whilst on the 

 ventral region anteriorly is a thick glandular investment 

 with numerous small blood-vessels at its inner edge, a 

 condition probably associated with a special secretion. In 

 order to follow the arrangement of the muscle it is necessary 

 to examine the extreme anterior end, where the dorsal 

 surface has a deep groove in the middle line, the rounded 

 parts on each side indicating the projecting dorsal muscles, 

 which already are large. The lateral regions are formed by 

 extensions of the body-wall, and bear the bristles in each 

 segment. A thin circular coat lies under the hypoderm 

 external to the dorsal longitudinal muscles, and it extends 

 into the lateral regions. Sections of the posterior end of 

 the ganglia lie below the great muscles, and in the mid- 

 ventral line is an elongated area between them. The ali- 

 mentary canal is clasped by strong circular muscular fibres, 

 the circular muscular coat of the body-wall being external 

 to it. In the middle line numerous vertical fibres pass 



* Jen. Zeitsch. Natur. xlviii. pp. 432-76, with 6 plates. 

 Ann. (& Mag. V. Hist. Ser. 9. Vol ii. 3 



