GEODIA AGASSIZII. 149 



the same region is inconsiderable (never over 13.3) and that the averages of the 

 differences between the specimens from locahties in different regions are pro- 

 portional to the distance between the regions. 



As in the case of the morphological aspect of the differences between the 

 pail's we also find, when examining them from this distributional point of view, 

 that these differences are regularly graduated: forms intermediate in struc- 

 ture, growing in places intermediate geographically, connect the very different 

 forms C and H occupying the two extremities of the stretch of coast off which 

 these sponges grow. 



This morphological and distributional continuity of the whole series of 

 forms renders it, in my opinion, advisable to consider the great differences of the 

 j^rotruding spicules as due to mere individual adaptation, and to place the 

 whole series in one species not divided into minor systematic units. 



Although I refrain from systematically separating the different forms grow- 

 ing in the different regions, I think that they might well be considered as 

 "incipient" varieties or subspecies, which, adapting themselves more and more 

 to the different peculiarities of their surroundings, may, and very likely will, in 

 coui'se of time, become systematically distinct — particularly if, through some 

 cause or other, they should disapj^ear from the central stretch of coast they now 

 inhabit. 



Of course there can be no doubt, that these sponges belong to the Geodidae, 

 but it is not so easy to decide the genus to which they should be assigned. As 

 some of their efferents are not covered by pore-sieves I was at first inclined to 

 place them in Sidonops. A careful investigation of the apparently uniporal 

 efferents made it highly probable, however, that these had, like the ones over 

 which sieve-membranes extend, been covered by such when the sponge was 

 alive and had been lost post mortem. For this reason I place these sponges in 

 Geodia. It is, in some cases, particularly when the specimens are not well 

 preserved, difficult to decide whether a geodid sponge with apparently uniporal 

 efferent apertures should be considered as a Sidonops or as a Geodia, and it is 

 jn-obable that some of the species placed by me ^ in Sidonops ought to be con- 

 sidered as species of Geodia. In studying the affinities of Geodia agassizii with 

 other previously described species, I have, for these reasons, compared it not 

 only with the sponges described as species of Geodia but also with those 

 described as species of Sidonops. 



The species of Geodia which have orthoplagiotriaenes, subcortical teloclades, 



' R. von Lendenfeki. Tetraxonia. Tierreich, 1903, 19, p. 100-101. 



