472 ALFRED GIBBS BOURNE. 



The capillaries upon the wall of the crop are solely develop- 

 ments of these extensions. 



The vessels of the walls of the gastro-ileal tube, the true diges- 

 tive portion of the canal, are directly derived from branches of 

 the lateral longitudinal vessels. 



The ventral sinus contains the nerve chain. 



The perinephrostomial sinus contains the nephridial funnel. 



The network of capillaries upon the testicular wall potentially 

 contain the testis. 



We now turn to the histological side of the question. 



The lateral vessels and their branches possess a very definite 

 muscular wall ; the smaller branches and capillaries only, have 

 no muscular development. 



The dorsal and ventral sinuses and their extensions never 

 possess muscular development, their walls consisting of con- 

 nective tissue ; the larger of them, the ventral sinus espe- 

 cially, may exhibit a large amount of pigmented tissue in the 

 wall. 



The botryoidal tissue is in reality composed of intracellular 

 tubes. 



The vaso-fibrous tissue is of the same nature, and it is such 

 tissue which forms the intermediate " cutaneous" network, i. e. 

 that which lies among the muscular tissue. 



The vaso-fibrous tissue and the botryoidal tissue are developed 

 from pigmented connective-tissue corpuscles and fibres, the 

 central portion of which liquefies, forming blood, the nuclei 

 forming corpuscles, the walls thinning out and forming thin- 

 walled capillaries, or it may simply become hollow, and allow 

 the blood in pre-existing capillaries to flow into them. 



Considering this double series of facts, it seems to me per- 

 missible to draw the following conclusions : 



The ventral and dorsal sinus and the extensions in connection 

 with these, either containing organs, e. g. the nerve-cord and 

 the nephridial funnels, or forming a complete network around 

 organs, correspond to a surrounding sinus in other genera, 

 and represent "coelom.^' 



The lateral vessels and branches represent a closed vascular 



