10 



shape l)el()ii^-ino" to the categories wliicli specialists call 

 "wai'ted spindles" (PI. TIL, tig-. 21), .lumb-hells (fig:. 22), 

 Ks (fig-. 2:!), and simple crosses. I'liey are formed in cells 

 fiiidded ofi' from the superficial ectoderm, and are only 

 newly formed at tlie snrface. This accounts for the fact 

 that they are always mrich moic crowded at the snrface 

 than they are in the more deep-seated parts of the colony, 

 and also for the fact that in the deeper parts the spicules 

 are always of full size. 



(ii.) The canals are seen most clearly near the snrface 

 of the colony (Plate I., fig. •)). They have a sinnons course 

 and appear to anastomose freely. They probably serve the 

 pniposes of disiributing' nonrishnienl and of maintaining: 

 an e((uilil)riuni in the watei' ])iessnr(> of the p<dyp cavities. 



(iii.) The fine lines, wliich hiok like ca})illary tubes, 

 really consist of string's or rows of cells. Thev have no 

 himen, and consequently cannot serve the purpose of 

 transmitting- the circulating fiuids of the body. AVe have 

 no definite knowledge of their function, but it is probable 

 that they are mainly concerned in the secretion of the 

 mesogloea. 



Anatomy of the Polyps. 



The structure of the anthocodia' can only l)e satisfac- 

 torily studied when they are fully expanded. AVhen re- 

 tracted the several organs are so tightly compressed that a 

 correct interpretation of their structure is quite impossible. 

 AVlien fully expanded each anthocodia exhibits a ter- 

 minal slit-shaped mouth (PI. I., fig. 4) surrounded by a 

 Clown of eight tentacles. The tentacles have a row of 

 short papilliform processes on each sid?, giving- them what 

 is called a pinnate form. The shape of the tentacles 

 changes every moment, slowly extending and retracting 

 or bending inwards and outwards as they are stimulated 

 1)V minute ijarticles fioatiny in the water. In the living 



