130 ERNEST WARREN. 



abundance in the tissues of certain Siphonophora, but I 

 have had no opportunity to compare them with the bodies 

 found occasionally in S. mediterranea. There is no evi- 

 dence, however, that the present bodies are really foreig'n 

 organisms. The greenish globules are gradually formed in 

 the cytoplasm of what appears to be a tissue cell of the 

 hydroid (text-fig. 1 , c). It is true that, in whatever tissue 

 the bodies may arise, there is a tendency for them to assume 

 the same oval shape and approximately the same size, but a 

 like tendency has been noticed in other cases where the 

 bodies do not mimic foreign organisms (cf. Sertularia 

 loculosa). At times in the ectoderm there is a marked 

 hypertrophy of the cells affected (text- fig. 7, b). The globules 

 (about 0'4ju in diameter) are produced gradually in the 

 cytoplasm, and the cell usually assumes an oval shape. 

 Ultimately the cell becomes densely crowded with the globules 

 and the chromatin of the nucleus is dissolved. Sometimes 

 the bodies are rounded, and the granules fuse together and 

 form a dead, brown mass (text-fig. 7, m). 



In Sertularia linealis Warren (text-fig. 8) the inter- 

 stitial cells of the ectoderm are aifected in clusters, and 

 chambered structures with blackened walls are formed, 

 resembling those found in the endoderm of Thuiaria 

 tubuliformis and Sertularia operculata. 



In Sertularia loculosa Bufih (text-fig. 9) certain cells, 

 both in the ectoderm and endoderm, become pear-shaped, 

 and there are gradually produced in the cytoplasm colour- 

 less globules of considerable size (about 0'8 fi in diameter) . 

 The nucleus clarifies owing to the solution of the chromatin. 

 Later, these globules become brown, fuse together, and 

 form a dead, homogeneous and characteristic mass (about 

 11^x4^) of yellowish-brown colour (fig. g). No trace of 

 nucleus remains. 



In Paragattya intermedia IFarre^i (text-figs. 10 and 11) 

 the pigmentation consists entirely in the blackening of reserve 

 food cells or yolk-cells which occur in the ectoderm among 

 the interstitial cells. No well-defined globules or pigment 



1 



