630 DR. J. S. BOWERBANK ON THE SPONGIAD^E. [May 7, 



stages of development. In their earliest state they appear as small 

 smooth spheres imbedded in a thick coat of gelatinoid sarcode ; and 

 in this condition the ovary measured jt^t i QC h m diameter. In 

 the next stage the diameter is considerably increased, and the infant 

 ovary is furnished with numerous long and acutely pointed spicula ; 

 and every gradation of its development may be traced until it attains 

 maturity. As it progresses in development the spicula appear to 

 become shorter and stouter, until in its fully developed and ex- 

 hausted state their distal ends are all cemented into a continuous 

 smooth mass, every distal termination having a completely truncated 

 appearance, and the whole mass having become as solid as a minute 

 sphere of glass. In this condition an average-sized one measured 

 -j-g^ inch in diameter. The greater portion of these organs in the 

 dermal crust are in the solid and exhausted state ; but on the ex- 

 ternal surface of the dermal crust there were many of them contain- 

 ing spherical masses of ova varying in size from about one fifth to 

 half the diameter of the ovary, and of a jet-black colour, and on some 

 of them I observed small patches of these exceedingly minute ova 

 spread over the surface of the ovaria, as if they had been just ejected 

 from those bodies at the time when the sponge was taken from the 

 sea. 



Pachymatisma areolata, Bowerbank. (Plate XLVIII.) 



Sponge massive, sessile, parasitical (?) ; surface uneven, full of large 

 deep areas or depressions. Oscula minute, numerous, congregated 

 in the deep areas of the surface. Pores inconspicuous. Dermis 

 crustular, rather thick, filled with ovaria ; furnished rather sparingly 

 with large acerate or acuate primary external defensive spicula, and 

 abundantly with small fusiformi-acerate secondary external defensive 

 spicula. Dermal membrane pellucid, furnished sparingly with small 

 fusiformi-acerate tension spicula ; and abundantly with very minute 

 and short fusiformi-cylindrical incipiently-spined retentive spicula, 

 and sparingly with large and small attenuato-stellate spicula. Ske- 

 leton — rete open and strong, entirely irregular ; spicula large, fusi- 

 formi-acerate, rarely acuate. Connecting spicula attenuato-patento- 

 ternate, large and strong, few in number. Interstitial membranes 

 — tension-spicula small, fusiformi-acerate, like those of the dermal 

 membrane, few in number. Retentive spicula the same as those of 

 the dermal membrane, very numerous. Ovaria subspherical, slightly 

 depressed ; reticulations of surface minute and delicate. 



Colour in the dried state cream-white. 

 Hab. The Red Sea (Mr. Hugh Cuming). 

 Examined in the dried state. 



I obtained this sponge from the late Mr. Hugh Cuming, who re- 

 ceived it, with other specimens of natural history, from the Red Sea. 

 It is a depressed mass of an irregular elongate-ovate form, 7 inches 

 in length, 3| inches in width, and 2| inches at its greatest thickness. 

 There is no basal attachment apparent, and it has every appearance 

 of having been unattached at the bottom of the sea for a consider- 



