54 CALIFORNIA ACADEMY OF SCIENCES. 



les parois du corps dans le manteau exterieur ; ces globules 

 ont perdu en partie leurs granulations graisseuses et se 

 sonl transformes en cellules voyagueses, puis ont forme 

 les cellules manteau," p. 6. He then says he has never 

 seen the direct passage of these " cellules amoeboides " 

 through the wall of the stolon. I am at a loss to know 

 why Kowalevsky does not recur to this in his recent 

 paper — whether he does not consider it a case in point, 

 or whether he had forgotten it. 



1 have never seen any indication of these cells per- 

 forming a phagocytic function such as is described by 

 Metschinkoff and Kowalevsky as taking place in the tests 

 of other Tunicates. A considerable variet}^ of foreign 

 bodies is found on the surface and imbedded within the 

 test of Perophora, but I have searched in vain for any 

 signs of their being surrounded or ingested by the test 

 cells. I have thought it possible that the unusual accu- 

 mulation of the cells at the point where the branchial 

 opening is about to form might mean that they are in 

 some way instrumental in effecting the breaking through 

 of the test. Of this I have no other proof, however, than 

 the mere fact of their numerous presence at this point. 



It seems to me that a sufficient number of cases suf- 

 ticiently widely distributed through the Tunicata are 

 now known to warrant the conclusion that a mesodermal 

 origin of the cells of the test is very general in the group. 

 However, with the large amount and excellent quality of 

 the positive testimony that the ectoderm gives origin to 

 them also, we are not justified in believing the mesoderm 

 to be their only source. It is worthy of notice, though, 

 that numerous writers, particularly recent ones, that 

 might be cited, have simply taken for granted their ecto- 

 dermal origin. 



I have no evidence that the matrix, or cellulose portion 



