25 



ning side by side (PL III., fig. 24). It passes through the test 

 substance of the longitudinal ridge downwards towards the base of 

 the colony. The lumen of these tubes is continuous with the 

 blood spaces of the zooid to which they belong. Their number 

 increases as they are traced downwards. They run mostly parallel 

 with one another and, so far as I could ascertain, there is no 

 anastomosing among them. In sections the vascular appendages 

 are found to be surrounded by a space separating them from the 

 test substance, but this is no doubt the result of contraction of the 

 neighbouring tissues. 



Reproductive Organs. Unfortunately in all the zooids examin- 

 ed by me the reproductive organs were not in full develop- 

 ment. Neither the testes nor the ovaries could be made out with 

 certainty. The genital duct, however, was tolerably large and 

 very clearly visible. This fact, I believe, renders it very probable 

 that the zooids examined by me had already passed through the 

 period of sexual maturity rather than that they were still on the 

 way of development. The duct runs along the rectum for some 

 distance and opens quite near the anus, somewhat covered over 

 by the expanded margin of that aperture. Its wall is lined with 

 cubical cells (PL IIL, fig. 22). 



Incubatory Pouch. In one of the colonies examined by me 

 nearly all of the zooids situated near the free margin of the head 

 are provided with an incubatory pouch . It is an appendage to the 

 mantle, being merely an enormous diverticulum of the peribran- 

 chial or atrial cavity. It is oblong in shape, nearly twice as long 

 as it is wide, and contains only a single embryo in the middle 

 where it is widest . The tadpole-like larva has three large adhesive 

 papillae and a long tail, and looks very much like that of Diplosoma. 

 Since the other colony, though somewhat larger, shows no indivi- 

 dual provided with a pouch, it is highly probable that the species 

 is dioeceous. 



Systematic Position. 



The external form of colony is, generally speaking, not a 

 character of much importance in determining the systematic posi- 



