732 IGEENA 11. J. S0LLA8. 



Large numbers of vesicular cells containing concretions are 

 to be found embedded on each of the above-mentioned 

 prominences of the test^ while in older kidneys there may be 

 a relatively enormous rounded mass of such vesicles more 

 deeply situated in the test substance (fig. 7, k.) . Some such 

 masses may be found in the basal layers of the test at a 

 distance from the abdominal cavity of any zooid ; these have 

 evidently been left behind, the zooid to which they belonged 

 having shifted upwards as the floor of the cloaca! cavity was 

 raised by the continual addition of fresh pellets. 



Thus the excretory organs of Hypurgon agree with the 

 simple type of excretory organ found in Botryllus, in that 

 the urinary concretions are stored in the cavities of single 

 vesicular cells ; but apart from this particular they are of a 

 type unlike any yet described (Dahlgriin, ' Archiv fur mikr. 

 Anat./ vol. Iviii, 1901) among Tunicates, and are far less 

 simple than any known in other Synascida. 



The reproductive organs lie in shallow depressions of the 

 wall of the abdominal cavity (fig. 9). The testis is oval, 

 and the vas deferens makes four or five turns of a spiral 

 around it. The ovary has membranous walls, and contains a 

 string of eggs of successive ages. I have not seen an oviduct. 



Any mature ova that I have seen have sunk deep into the 

 test, and so have come to lie in a great recess of the abdomi- 

 nal cavity (fig, 10), communicating with it by a narrow 

 aperture. The material contains but one larva, which was 

 developing in a completely closed cavit}^ in the test (fig. 11). 

 This may or may not be the normal course taken by the 

 dovoloping eggs. Eggs are not to be seen being sheltered 

 by any other part of the organism than the test, though eggs 

 of all ages were found in the ovaries. 



The faecal pellets, which contribute so largely to the 

 formation of the test, show a very remarkable degree of 

 coherence. If a piece of the colony be boiled in sulphuric 

 acid, the residue consists of f^cal pellets which retain their 

 form perfectly, and continue to do so even if the boiling bo 

 mnch prolonged. Even thin sections of pellets, isolated by 



