508 MAYNARD M. METCALF, 



The cells of the gland in Ecteinascidia show clearly a remarkable 

 histological character that in most other species is not so plainly 

 seen. The gland cells are large and easily studied. Fig. 12 of 

 Plate 34 shows a single cell. Its nucleus is pushed to one side by 

 a large vacuole which almost completely fills the cell body. Within 

 the vacuole is seen an irregular coagulated mass ^), which stains with 

 Delafield's haematoxylin less deeply than does the cell protoplasm. In 

 many cases the nucleus is distorted by the pressure of the vacuole 

 into a slender semi-lunar disc. Both the cells of the endothelium 

 and their derivatives, the cells filling the lumen of the gland, show 

 this peculiar character. The latter are found in different stages of 

 degeneration. One naturally regards the vacuole contained in each 

 of these cells as a vacuole of secretion, but instead of this being 

 poured out from the cell, and the cell then proceeding to form another 

 similar vacuole, the whole cell disintegrates. Important for comparison 

 with these conditions is the state of the gland in Polycyclus renieri 

 to which reference will be made later (cf. p. 523 and p. 528 to). 



Perophora viridis Verr. 



Plate 34, Fig. 13. 



PerojjJiora viridis shows the same sort of vesicular cells as have 



just been described for Ecteinascidia, and in other regards the anatomy 



of the gland and ganglion and their outgrowths is similar in the two 



species. 



Clavelinidae, Summary and Comparisons. 

 So far as the anatomy of the intersiphonal organs is concerned 

 the five species of this family described fall into two groups. The 

 first group, containing Rhopalaea neapolitana, ClaveUina rissoana and 

 Diazona violacea, closely resembles the Ciotiinae among the Ascidiidae 

 in the presence and manner of arrangement of the rapheal nerve. 

 The other group including Ecteinascidia iurbinata and Perophora 

 viridis, differs markedly from the other three forms in the total ab- 

 sence of any rapheal duct. In this regard they more nearly approach 

 the sub-family Ascidiinae in which the rapheal duct, though present, 

 is but imperfectly developed. Perophora and Ecteinascidia also agree 

 in the vesicular character of their gland cells, a feature which, if 

 present at all in the other three species, is much less marked. 



1) The material was killed in Perenyi's fluid and preserved in 

 alcohol. 



