54 ANATOMY AND PHTSIOLOGT 



of the sponge, and affording ample space for the imbed- 

 ment of such spicula in its substance, I am, therefore, 

 induced to think it probable that a similar abundance 

 of sarcode may exist in Lactylocalyx and other similarly 

 constituted sponges, and that hereafter even the largest 

 of this tribe of spicula will be found completely imbedded 

 in the sarcode. 



Slender attenuated rectangulated hexradiate (Fig- 184, 

 Plate VII). — Beside the large and stout attenuato- 

 hexradiate spicula in Eiqilectella aspergillum, there are 

 comparatively small and very slender ones, many of which 

 are nearly of the same proportions as the larger ones ; but 

 generally speaking the axial radii are more elongated, 

 and in some cases the basal end is extended to four 

 or six times the length of the apical portion. 



These spicula do not present the same irregularity in 

 their development that we observe in the stout ones, 

 and it is a rare occurrence to find one without the full 

 number of rays. They are exceedingly numerous in the 

 sponge, and they occur in closely packed fasciculi, the 

 axes of the spicula nearly touching each other. Amidst 

 these fascicuH we find the large stout forms imbedded, the 

 whole of them apparently having been completely enveloped 

 by the sarcode of the sponge. 



Cylindro-rectangulated hexradiate : apically spined (Fig. 

 185, Plate VII). — This form is very abundant in an 

 undescribed species of Alcyoncellum in the Museum of 

 the Jardin des Plantes, Paris. The figure represents 

 the upper portion of the spiculum only, the lower portion 

 of the axial shaft being exceedingly elongated. When 

 examined with a power of 400 linear, the apices of the 

 radii are seen to be abundantly, but minutely spined. 

 The axial shaft of this spiculum, without any of the lateral 

 radii developed, is also abundant ; it is exceedingly long, 

 and at the proper distance below the apex we often observe 

 a gradual enlargement of the diameter, as represented in 

 Fig. 187, and the rudimentary canals for the lateral radii 

 are frequently apparent. 



This form of spiculum is also very abundant in Bac- 



