DESCRIPTION OF EPHYDATIA BLEMBINGIA. 105 



EXPLANATION OF PLATES 1—4, 



Illustrating Mr. Richard Evans' paper on " Epbydatia 

 blembiugia, and the Development of the Genimule in 

 the same Species." 



All the figures from 2 — 17 a, botli inclusive, liave been drawn with tlie 



camera lucida. 



Significance of the Lettering. 



am. wand. cell. =.ful.yo. cells. Amoeboid wandering cells which later on in 

 the development becoiDC the yolk-cells. Am. wand, cells = fut. col. cells. 

 Amoeboid wandering cells which later on in the development become the 

 columnar cells. Amphid. Amphidiscs. chit. sept. Chitinous septum, col. 

 cells. Columnar cells, col. lay. Columnar layer. d.m. Dermal membrane. 

 in. chit. lay. Inner chitinous layer, nu. Nucleus, ou. chit. lay. Outer chiti- 

 nous layer, mod.sclerob. Modified scleroblast or spicule cell, sclerob. Sclero- 

 blast, s.d.c. Sub-dermal cavity. spic. Spicule. sp.Jilj. Spicule fibre. 

 tropho. Trophophore. v.s. Vegetable support of the sponge. yo.body 

 Yolk-body. yo. cell. Yolk-cell. 



PLATE 1. 



Fig. 1 (x li).— Ephydatia blembingia growing on vegetable supports, 

 V. s. 



Fig. 2 (x 28). — A section showing diagrammatically the structure of the 

 sponge, especially the deimal membrane {d.ni.) and its supports, which are 

 traversed by the spicule fibres; the large sub-dermal cavities {s.d.c); the 

 poorly developed spicule fibres {sp.fib.), the great number of spicules, both 

 amphioxea and amphidiscs, scattered about more or less loosely in the 

 tissues, and the gemmules {gem.) which are never found aggregated together 

 in groups. 



Fig. 8 (x 225). — A representation of the various kinds of spicules, a — e 

 represent the amphioxea which on the one hand form the spicule-fibres, and 

 ou the other hand lie about loosely in the sponge-tissues. / is one of the 

 s])icules which are seen grouped together in fig. 7. g — i are the ampiiidiscs. 

 ^ and h are fully formed; < and k are intermediate in size, while / and m 

 represent the early stages. 



Fig. 3 was drawn from specimens cleaned with nitric acid. 



Fig. 4 (X 575).— A more highly magnified representation of souie of the 



