STRUCTUEB OF THE LAEVA OF SPONGILLA LAOUSTRIS. 449 



The second class of authors may be further subdivided : by 

 some the inner mass is supposed to give rise to the collar- 

 cells as well as to the rest of the sponge — the view held by 

 Gotte (5) and Noldeke (13) ; while according to another view, 

 supported by Delage (1) and by Maas (8) in his later paper, 

 the inner mass only gives rise to the '' dermal layer/' including 

 in that term the amoeboid cells. 



Since the views of Ganin and Maas (7) are practically 

 the same with regard to the structure of the inner mass 

 and the fate of its constituents, it will suffice to discuss 

 Maas' account alone. Before making any statements with re- 

 gard to the above account it is necessary to refer to Delage's 

 criticism of it, but for the present I shall reserve what I have 

 to say on Delage's views of the structures described by Maas 

 as flagellated chambers. 



Delage says that the larvse observed by Maas are abnormal, 

 or rather unusual and pathological. I have shown in the 

 account already given that the larvse which Delage describes 

 as abnormal are capable of developing to the adult sponge. 

 He is, therefore, not justified in describing such a larva as a 

 pathological one incapable of righting itself. The larva in 

 question is not an abnormality, but a variety, which is 

 capable, and also does give rise to the same end result as 

 Delage's normal larva, which is the same as type D of the 

 present account. 



The chief peculiarity of both Ganin's and Maas' view of the 

 development of the flagellated chambers is that they derive 

 them from the layer of flattened cells ("endoderm") which 

 lines the larval cavity. The " endoderm " grows out into the 

 layer which intervenes between it and the flagellated '^ ecto- 

 derm," i. e. into the " mesoderm " of the triploblastic larva. 

 The swollen or expanded end of the evaginations in question 

 are held to be the flagellated chambers, while the intervening 

 canals become the exhalant system. What is peculiar about 

 this view is that it is absolutely right as to the fate of the 

 parts in question, but equally wrong as to their origin. It 

 appears that Maas' mind was at that time so dominated by the 



