222 CCELENTERATA. 



E. aspergillwm O\vcn. Philippines. In the body cavity of the glassy sponge 

 are found Acf/a spongipliila, and a small Pdltrmon. Hijtilonrtnn S'lelidldil 

 Gray, Japan. //. liarcale Loven, North Sea. 



Order 5. C ALOIS PONGI.E, Calcareous sponges. Usually colour- 

 less, sometimes red-coloured sponges and sponge stocks, the skeletons 

 of which consist of calcareous spicules. These are either simple 

 needles (as they first appear in the embryonic form) or three or four- 

 armed cross spicules. Very often, however, we meet with two or all 

 three forms of spicules in the same sponge. 



* 

 Fam. Asconidae (Leucosolenidee, Ascons). Calcareous sponges, the walls of 



which are pierced by simple canals. Grant la Lk. (Lntrosolenin Bbk.). these 

 are divided by E. Haeckelinto seven genera, Ascyxsa, Axcctta, Axcilla, Axcortis, 

 Axriilmis, Axcaltix, Aftcandm, accordingto the form of the calcareous needles or 

 spicula. Gr. botryoides Lk. (Axrandra complicata, E. Haeck). Heligoland, 

 nearly allied to Gr- LiclcrliiUniii 0. S. from the Mediterranean and Adriatic. 



Fam. Leuconidae (Grantiidee, Leucons), calcareous sponges, with thick wall, 

 which is pierced by branched channels. Li-nconin- Grt. , divided by E. Haeckel 

 into seven genera, according to the form of the calcareous spicules Leucijxxtt, 

 Lcucetta, Lc-ucilln, Lmicortix, Lrucnlmix, Li'itraltix. Lcucandru. L. (Lnu-cttii) 

 j)rlmi(jcn/a E. Haeck. 



Fam. Sycondiae (Sycons). Mostly solitary calcareous sponges, with thick 

 walls, which are pierced by straight radial tubes. The latter project on the surface 

 as conical prominences of the wall. Xi/ron Eisso, divided by E. Haeckel into 

 seven genera tii/ei/ftsa, Si/cettti, Si/rillu. tfi/corfis, Si/ciilniix. Xi/cnltix, Syrandrii. 



SUB-GROUP II. CNIDARIA (C(ELENTERATA, s. str.) 



Cadenterata, with consistent tissues not pierced by a system of pores ; 

 the osculum is replaced by a mouth ; with thread cells in the epithelial 

 tissues. 



The Cnidaria represent the Coelenterata in a more restricted sense ; 

 and in their structure the radial symmetry appears more strongly 

 marked. In them the amoeboid cell, as an independent tissue unit, 

 loses its importance for the functions of locomotion and nourishment, 

 although the entoderrn cells often possess the power of absorbing 

 solid particles, after the manner of the amoeba? . The gastrovascular 

 apparatus, on the contrary, functions distinctly as a digestive and 

 circulatory body cavity. Pore systems in the skin are not required 

 for the introduction of nourishment, since the mouth, which corre- 

 sponds to the osculum, provides for the reception of food. ISTemato- 

 cysts are very commonly found as productions of the epithelial cells, 



