324 WILSON. [Vol. IX. 



neben den Doppelkeulchen mit glatten Kopfen solche, wo auf 

 dem Scheitel des Kopfes einige klcine Knotchen entstehen. 

 Diese letztere Form nimmt in einzelnen Individuen iiberhand, 

 und ist in noch anderen ausschliesslich vorhanden." All the 

 individuals of Tedania B. examined agreed in this respect, and 

 it seems proper here to regard the nicked head as a specific 

 characteristic. Tylotes are found free and scattered about in 

 the gelatinous tissue. Round the subdermal cavities of this 

 tissue they form loose bundles which follow the curves of the 

 cavities, PI. XIX, Fig. 61. The brushes of tylotes which support 

 the dermal membrane have mixed with them a number of 

 microscleres (oxeas). Crossing the meshwork of spicules and 

 pursuing an entirely independent course, are found here and 

 there a few long and slender skeletal bundles consisting largely 

 of tylotes intermingled with oxeas. The oxea, PI. XX, Fig. 6jb, 

 aside from the situations just spoken of, is found in abundance 

 in the gelatinous tracts where it varies in size, as has been 

 mentioned, from the dimensions figured to those of a micro- 

 sclere, the latter form being especially common round the 

 walls of the larger efferent canals. The skeletal meshwork is 

 made up exclusively of strongyloxeas, which are all as is shown 

 in Fig. 67 a, slightly bent. I have spoken of this meshwork 

 as confused. It is confused in the first place because the 

 spicules are so closely packed, that the meshes are not bounded 

 by single spicules but by little bundles. And in many places 

 it so happens that the spicules are arranged in such a way that 

 they both bound the meshes and help to form a continuous 

 skeletal bundle. Two such bundles are shown in I'ig. 61, 

 which fairly well represents the meshwork of spicules. 



The homology between pores and oscula upheld by Barrois 

 (I) and others, receives perhaps some additional support from 

 the occurrence in Tedania of such openings as those shown in 

 PI. XX, Fig. 68 (a small portion of the surface). These open- 

 ings lie in the gelatinous furrows, and in their immediate neigh- 

 borhood there are but few pores. They are larger than the 

 pores, but very much smaller than the ordinary oscula, and may 

 therefore be classified as structures intermediate between the 

 two. 



