48 ANATOMY AND PHYSIOLOGt 



the obtuseness of their terminations, as represented in 

 Pig. 144, Plate VI. We next find the same form increased 

 in strength, and with slight lateral fimbriae near each end 

 of the shaft at the commencement of the hami, as in Pig. 

 145, Plate VI. In a more advanced state we find a 

 regularly curved extension of the fimbriae, slightly so 

 at one extremity of the shaft, and considerably so at the 

 other ; and as the development progresses, the curves 

 of the fimbriae are extended in an outward direction, and 

 become angular; the extremities of the hami expand 

 laterally and assume a foliated appearance, as seen in 

 the distal or larger end especially (Pig. 146, Plate VI), 

 but the fimbriae at the smallest or proximal end of the 

 spiculum, and the foliated extremity of the adjoining 

 hamus, are stiU separated from each other; and this 

 progressive development may be observed in all its stages, 

 untU the connexion of the parts is completed, and the fully 

 developed form represented in Pig. 147, Plate VI, is 

 produced. The same progressive development of this form 

 of spiculum may be traced in those of Hymeniacidon lingua, 

 Bowerbank, from the Hebrides. 



In the performance of their natural office in the sponge, 

 we find the same laws of attachment and projection obtain 

 that I have described in treating of the bihamate spicula. 

 In the equi-anch orate forms, where the terminal palms 

 or teeth are equally developed, the shaft is attached by the 

 middle of the external curve ; but in the inequi-anchorate 

 forms, where one palm is developed to a very much greater 

 extent than the other, we find the smaller one is attached 

 to the membrane, and the larger is projected at about 

 an angle of 45 degrees. Generally speaking, the ancho- 

 rate spicula, like the bihamate ones, are irregularly dis- 

 persed over the surface of the membranes, but occasionally, 

 as in Hymeniacidon lingua, they are developed in circles or 

 rosette-formed groups. 



In many cases these groups contain so large a number of 

 spicula as to render any attempt to count them ineffectual, 

 and m some instances so many are developed that the 

 group assumes the form of a baU rather than that of a 



