2o6 



PORIFERA 



■of basalia. The upper end of the tube is closed by a sieve 

 plate, the perforations in which are oscula, while the beams 

 contain flagellated chambers, so that the sieve is simply a modified 

 portion of the wall. It is a peculiarity of 

 this as of one or two other allied genera 

 that the lateral walls are perforated by 

 oscula. They are termed parietal gaps, 

 aiid are regularly arranged along spiral 

 lines encircling the body. 



Ijima, who has dredged Euplectelffls 

 Fig. 99.— Sieve plate of from the waters near Tokyo, finds tlpit 

 (.\fter ijiriia.) ^^ joii^g Specimens oscula are confined to 



the sieve plate ; parietal gaps are secon- 

 dary formations. The groundwork of the skeleton is a lattice 

 similar to that shown in Fig. 100. The chamber-layer is much 

 folded. Various foreign species of Euplectella afford interesting 

 examples of association with a Decapod Crustacean, Spongicola 

 venusta, of which a pair lives in the paragaster of each specimen. 

 The Crustacean is light pink, the female distinguished by a 

 green ovary, which can be seen through the 

 transparent tissues. It is not altogether 

 clear what the prisoner gains, nor what fee, 

 if any, the host exacts. 



Ijima relates that the skeleton oi Euplec- 

 tella is in great demand in Japan for 

 marriage ceremonies. He also informs us 

 that the Japanese name means " Together 

 unto old age and unto the same grave," 

 while by a slight alteration it becomes 

 " Lobsters in the same cell," and remarks 

 that the Japanese find this an amusing pun. 

 The same Spongicola lives in pairs in 

 Hyalonema sieioldi. Another case of fio. lOO.— Skeletal lattice 

 apparently constant association is that of of £npiecteUai,nperialis. 



'■^ •' After Ijiina.) 



the Hydroid stocks which inhabit Walteria. 



F. E. Schulze describes Stephanoscyphus mirabilis (see p. 318) in 

 a specimen of Walteria flemmingi ; the presence of the polyp 

 causes the sponge to grow out into little dome-shaped elevations, 

 each of which shelters one polyp ; while in W. leuckarti Ijima 

 finds a similar association in every specimen examined. 



