DEEP SEA FAUNA 1307 



other rhizopods, radiolarians, and sponges; and we 

 as yet know very little of the life-history of these 

 groups. 



Many foraminifera of different groups inhabit 

 the deep water, lying upon or mixed in the upper 

 layer of the globigerina ooze, or fixed to some foreign 

 body, such as a sponge, coral, or stone; and all of 

 these are remarkable for their large size. 



The few hauls of the dredge which we have al- 

 ready had in deep water have been enough to teach 

 us that our knowledge of sponges is in its infancy- 

 that those which we have collected from shallow 

 water along our shores, and even those few which 

 have been brought up from deep water on fishing 

 lines, and have surprised us by the beauty of their 

 forms and the delicacy of their lustre, are the mere 

 margin and remnant of a wonderfully diversified 

 sponge-fauna which appears to extend in endless va- 

 riety over the whole of the bottom of the sea. 



The most remarkable new forms are referable to 

 the group which seems to be in a sense special to deep 

 water, the Hexactinellidae. One of the most abun- 

 dant and singular forms belonging to this order, 

 Holtenia carpenteri, is an oval or sphere 90 to 100 

 mm. in height, with one large oscular opening at 

 the top about 30 mm. in diameter, whence a simple 

 cylindrical cavity cupped at the bottom passes down 

 vertically into the substance of the sponge to the 

 depth of 55 mm. The outer wall of the sponge con- 

 sists of a complicated network of the cross-like heads 

 of five-rayed spicules. One ray of each spicule dips 

 directly into the body of the sponge, and the other 



