OF THE SPONGIAD^E. 251 



FIG. 



adult ones have the terminations of the hami 

 strongly produced, as represented in Fig. 141, 

 while in the immature spicula, although the palms 

 are fully produced, the tooth appears in a rudi- 

 mentary condition, as Fig. 142, Pages 46 and 47. 



144. DENTATO-PALMATE INKQUI-ANCHORATE. X 260 



linear. First stage of development. Page 48. 



145. DENTATO-PALMATE INEQUI-ANCHORATE, second stage 



of development. X 260 linear. Page 48. 



146. DENTATO-PALMATE INEQUI-ANCHORATE, third stage of 



development. X 260 linear. Page 48. 



147. DENTATO-PALMATE INEQUI-ANCHORATE, an adult 



spiculum, showing the fully-produced distal ter- 

 minal hastate tooth. X 260 linear. Page 47. 

 See also Fig. 297, Plate XVIII, for the same form 

 of spiculum in sitit, from Hymeniacidon lingua, 

 Bowerbank. X 308 linear. 



148. DENTATO-PALMATE INEQUI-ANCHORATE. From the 



same sponge as Fig. 147, showing the effects of 

 incomplete development or malformation. X 260 

 linear. 



149. EXPANDO-TRIDENTATE EQUI-ANCHORATE. X 1250 



linear. From an undescribed sponge in the 

 British Museum. The shaft is frequently curved 

 to the extent of nearly a semicircle. Expando- 

 bidentate forms are mingled with the tridentate ones. 

 150. TRIDENTATE FIMBRIATED EQUIANCHORATE. X 660 

 linear. From Isodictya Jimbriata, Bowerbank, 

 Shetland. The spicula of this form may be traced 

 from the earliest stage of development, with 

 scarcely a trace of fimbriation to the adult spicu- 

 lum. Fig. 150. They are very abundant on the 

 interstitial and dermal membranes, and mixed with 

 them there are many that are only bidentate, but 

 which are as completely nmbriated as the tri- 

 dentate ones. The fmibrise are very delicate and 

 translucent, and require a careful management of 

 the light to render them apparent. 



