PLATE 3(3. 



Reconstruction of posterior end of Chaetodernia argentea. 

 2. Same of Chaetodernia attenuata. 



Advanced stage in spicule development, the matrix cells retaining their attachment to 

 Proneonienia hawaiiensis. X 555. 

 Somewhat earlier stage than fig. 3. X 555. 



Completion of sjiicule development and commencement of shifting of matrix cells. X 555. 

 Reconstruction of anterior end of Strophomenia triangularis. 

 Early stage in development of spine in Proneonienia hawaiiensis. X 555. 

 Hypodermis in Limifossor fratula. X 255. 

 Posterior end of Alexandromenia agassizi. X 3. 

 Pajiilla and outlet of .salivary gland in A. agassizi. 



Very early stage in development of spine in Proneomenia hawaiiensis. X 555. 

 Blood corpuscles of Strophomenia scandens. X 450. 

 Same of Chaetodernia hawaiiensis. X 4.50. 

 Same of Lophomenia spiralis. X 450. 

 Spines of Strophomenia triangularis. X 150. 

 Same of Strophomenia spinosa. X 205. 

 Same of Strophomenia ophidiana. X 205. 



Completed development of radially directed spine of Proneomenia hawaiiensis; and 

 developing papilla. X 555. 



Fig. 19. Base of gill plates and attached gland cells (gc), Alexandromenia agassizi; ne, nerve. 



