30 F. W. GAMBLE AND J. H. ASHWORTH. 



nephridia, and there is no trace of carmine in the coelom after 

 forty-eight hours.^ 



Coeloraic Corpuscles. — These abundant cells occur in 

 two chief forms, which probably pass into one another. The 

 first varies from 8 to 20 ju in length, is amoeboid, and usually 

 contains yellow or brown granules of a very highly refractive 

 character. The pseudopodia are often grouped at the two 

 ends of the cell (PI. 5_, fig. 24). The longer forms of this kind 

 of corpuscle pass into the second or spindle-shaped cells of the 

 ccelom, which measure as much as 50 /x in length, and contain 

 no coloured granules. These fusiform elements are most abun- 

 dant, and constitute the most characteristic features of the 

 ccelomic contents. 



The chlorogogenous tissue of the ventral vessel and its 

 branches in the body-wall consist of groups of cells about 20 fi 

 in length, full of large slightly yellow or deep brown granules, 

 which are not highly refractive. The tissue in old black 

 worms is immensely developed, so as to completely cover the 

 vessel by the masses of hair-like threads, each thread consist- 

 ing of a small blind diverticulum of the vessel surrounded by 

 the chlorogogenous cells. 



11. Reproductive Organs. 



Thanks to the researches of Cosmovici (1880), Cunningham 

 (1887), Kyle (1896), and others, the true ovaries and testes of 

 Arenicola marina are now known to arise by proliferation 

 of the peritoneal covering of an extension of the blood-vessel 

 supplying the funnels of the nephridia. It is not certain that 

 there is a corresponding gonad on the first pair of nephridia, 

 but on each of the following five pairs the gonads are present 

 during the breeding season. In both sexes the organ is a mass 

 of cells, from which the ova or spermatoblasts break away at 

 a very early stage, to ripen in the coelom. The rachis is con- 

 tinuous with the posterior angle of the nephrostome, and is 

 developed around a backwardly projecting process of the 



' Schneider, 'Arbeit. Naturf. Gesellschaft,' St. Petersburg, Bd. xxvii, 

 Heft 1, 1890. 



