526 ORESSWELL SHEARER. 



directions by irregular strands and muscular fibres. About 

 the gut it forms a sort of sinus in which a few large orange- 

 brown granules are constantly seen (see fig. 3, e.gr.) ; these 

 move up and down it from one end of the stomach to the 

 other as the worm twists and bends. Roughly, the contour 

 of the space follows the general form of the external segmen- 

 tation, sending prolongations towards the surface at the end 

 of each segment, which augment the marked pseudo-metameric 

 appearance of the animal when seen under the microscope. 

 That this space cannot be strictly regarded as a coelomic 

 cavity is amply testified by the fact that the spermatozoa are 

 seen enclosed in an entirely different set of spaces lined with 

 a definite membrane, by no chance ever being seen in this 

 space or any of its numerous prolongations into the general 

 mass of the testis tissue (fig. 4, sjj.m.). Also by the fact that 

 it is traversed in all directions as already mentioned by 

 numerous muscle-strands and cells which denote its primitive 

 blastocoelic nature. It seems to me this space is directly 

 comparable to the great blastocoelic cavity of the head-segment 

 of the Polygordius larva, into which the larval nephridia 

 project with their solenocytes, but with which their canals do 

 not communicate, and to the blastocoelic collar space of the 

 Actinotrocha larva, into which their larval organs project 

 under similar conditions ; the space that subsequently gives 

 rise to the circular blood-vessel ring of the adult in this 

 animal. 



In Dinophilus this cavity sends two prolongations from 

 the corners of the stomach forward into the head region, 

 these run outward to terminate in two small triangular en- 

 largements beneath the skin a short distance behind the eyes 

 (fig. 14, hic.l). These spaces are shown partially on either 

 side of the oesophagus (fig. 15). Into these the heads of the 

 first pair of nephridia bearing the solenocytes project, the 

 solenocytes standing out on the end of the nephridial canal 

 into the lumen of the space like bristles from a brush (fig. 1). 

 The protoplasmic parts of the solenocytes are but imperfectly 

 seen on account of their transparent nature, and their presence 



