109 



The results are valuable, because they so definitely point to 

 the existence of two perfectly distinct modes of growth, almost 

 two varieties, in the species as well as the ordinary continuous 

 and vegetative vanations. Type i also shows the presence in a 

 single habitat of small though perfectly discontinuous variations 

 in the colouration of its septa, variations not found in type 2 nor 

 in the young. Some are colourless, others have the septa of 

 cycles I. and II. black, and yet others have all the septa black. 

 In some the septa of cycle I. are blacker than those of cycle 

 II., and in yet others cycle IV. septa have not as yet attained 

 their colouration. When the caHcle is looked at from the 

 surface, the spiral chamber in which the Aspidosipkon lives 

 runs from right to left in most cases, but in a certain number 

 from left to right. In 50 specimens that I have ground down 

 a shell is present in each. In one of a left to right spiral, the 

 difference was due to the shell being sinistral, but in two others 

 examined I could not determine with certainty their character, 

 though both seemed to be dextral. The Aspidosipkon cham- 

 ber commonly has, in addition to its large opening to the ex- 

 terior, a second very minute op>ening on the under side of the 

 corallum, close to the mouth of the shell it originally inhabited. 

 This is, I believe, normal, but in 30 or 40 per cent, of the speci- 

 mens there are 2 or more of the small openings, the additional 

 ones lying along the spiral tube of the commensal. 



in addition to the specimens "already referred to, four speci- 

 mens, all belonging to type 2, show fission of the calicle, or 

 possibly in two cases budding from within the calicle (see PI. 

 III., figs. 35-38). A fifth specimen, belonging to type I, had 

 become killed over the greater part of its calicle, but the re- 

 mainder budded out a fresh caUcle, which now stands up on a 

 broad base, situated on the parent cup. The dead specimens, 

 of which over 100 were obtained in dredging i, do not differ in 

 size from types i and 2 as described, none belonging to the 

 third or young series ; they bear the same proportion, nearly 4 

 to I, that these types have to one another. 



C 



