394 Mr. H. J. Carter on 



Delicate as these spun -glass-like Hexactinellida appear to 

 be, their resistance to destruction is very remarkable, owing 

 to the toughness which is imparted to the silica by the pre- 

 sence of the albuminous element and the intricate union of 

 their reticulated fibre, so that, while the thinner superstruc- 

 ture even of Farrea occa, when reduced to a single layer, is 

 much tougher than it looks, the base, thickened with the ad- 

 ditional matter, becomes almost unyielding. Hence, probably, 

 these parts of Farrea occa alone are left in much-worn 

 specimens at the bottom of the sea, and thus constitute the 

 fragments which are often brought up in " swab " dredging 

 without the superstructure. 



Such resistance to destruction and the reparation of the 

 most delicate parts which are essential to the life of the organ- 

 ism often indicate the presence of a preservative power which 

 is far greater than we think, but how it should be so under 

 the circumstances is utterly beyond our comprehension. Per- 

 haps some might say that this pertinacity of vital force has 

 been acquired by long progress in a certain direction, upon 

 the principle of " vires acquirit eundo ;" but then, how did 

 the Jirst impetus come about? 



I should also add that this specimen of Farrea occa had 

 been infested by a minute parasitic Hydroid, whose delicate 

 stolonic coenosarc, together with its small sessile polypites, 

 had thickly spread in and over the outer surface ; but at pre- 

 sent it is so hard and shrunken from desiccation that, beyond 

 the presence of thread-cells and the general form, there is no 

 possibility of arriving at more specific characters. Lest the 

 dark round points in the illustration (PL XII.) should be 

 mistaken for holes or vents, it should be mentioned that they 

 represent the polypites of the Hydroid. 



Periphragetta ENsce, Marshall. 



Club-shaped, stipitate, hollow, cup-like, with extended base 

 of attachment ; slightly bent upon itself ; wall thick, com- 

 posed of tubo-branched, anastomosing, often dividing, laby- 

 rinthic, clathrous structure, whose interstices within form 

 fenestral openings in the sides of the excavation, and whose 

 outer part, especially in the lower portion, passes into a much 

 smaller tubo-reticulated structure of the same kind, which, 

 becoming diminished in size towards the surface, terminates 

 there in still smaller branches, whose ends are free and open ; 

 stem round, short, descending upon an expanded, wide, 

 arched, irregular, flat foot below, and above into the structure 

 mentioned ; the open state of the terminal branches of the 

 smaller tubo-branched structure is apparently natural, from 



