Hyatt.] 84 [March 6, 



and Sycaltis ovipara (ibid. p. 275, pi. 47) is interesting in this 

 connection, but whether contradictory or confirmatory of our 

 suggestion cannot now be determined. 



An elliptical opening also appeared in the chorion of Hal. in- 

 crustans, through which the cells of the embryo escaped when 

 under sufficient pressure A similar opening, supposed to be a 

 micropyle, was also seen in Suberites in the multicellular morula, 

 but with the rim much thicker than the walls of the chorion 

 layer. It becomes interesting to note also, that this layer 

 absorbed aniline, like the soft keratocle of the young fibres, of 

 Ohalinula, when staining was tried in a species of Isodictya, and 

 when viewed from the side in Halichondria the impression wa§ 

 that the cells contained highly colored keratode in a granular 

 form, and that the walls of these cells were more or less stiff- 

 ened or affected by internal deposits of some sort. The walls, 

 however, did not seem to absorb color in the same degree and 

 behaved more like the older keratode of the fibre in Chalinula. 

 This result cannot be considered satisfactory, but the membrane 

 is tough and essentially protective. 



The use of the blastoporic area as a larval base of attachment 

 enables us to account for the variety of ways in which the embryo 

 carries itself, and becomes attached. In some forms any part of 

 the body may serve as the base, and in Reniera filigrana, as stated 

 by Marshall, the embryo may even reverse the usual position and 

 in moving, carry the blastoporic area in front and become 

 attached habitually by the posterior or primitive cloacal end. 

 This is easily understood if we grant that the function of attach- 

 ment is a secondary or acquired habit, not a primitive use. It 

 would be liable to great variation and some larvae might entirely 

 revert to the primitive position in moving and in becoming 

 attached as in R. filigrana. 



As regards the opposite pole it may be readily observed that 

 the ectoderm is in all the earlier stages continuous. Mar- 

 shall (Zeitschr. Wissen. Zool. 1882, vol. xxxvn, pi. 13), has figured 

 the aboral pole of the larva as being open, and plugged with the 

 internal cells which have broken through as at the other pole. 

 This aperture in the ectoblast, which is the primitive cloacal open- 

 ing, we have seen plainly in Spongia graminea, with the inter- 

 nal cells protruding and continuous with the internal con 



