206 



PORIFERA 



CHAP. 



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

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

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

 portion of the wall. It is a peculiarity o: 

 this as of one or two other allied gener 

 that the lateral walls are perforated b; 

 oscula. They are termed parietal gap 

 and are regularly arranged along spira 

 lines encircling the body 



Ijima, who has dredged Euplectellid 

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



Euplectella imperialis. i n i , 



(After ijima.) ln y oun o specimens oscula are confined t 



the sieve plate ; parietal gaps are secon 

 dary formations. The groundwork of the skeleton is a latti 

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

 folded. Various foreign species of Euplectella afford interestin 

 examples of association with a Decapod Crustacean, Spongicol 

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

 The Crustacean is light pink, the female distinguished by 

 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 of 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 sieboldi. Another case of Fig. 100 

 apparently constant association is that of 

 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. 



Skeletal lattice 

 of Euplectella imperialis. 

 After Ijima.) 



