170 ANATOMY AND PHYSIOLOGY 



strong, thick- shelled, more or less globose ovarium, having 

 a funnel-shaped orifice at the apex, which communicates 

 with the central cavity, which, in the prolific state, is filled 

 with closely-packed minute vesicular bodies, very similar in 

 appearance to those contained in the ovaria of the Spon- 

 gillida?, but apparently more minute. In this condition of 

 the ovary its parietes are formed of acutely cuneiform 

 spicula, firmly cemented together by siliceous matter, the 

 united apices forming the inner surface of the ovarium, 

 while the united truncate bases form the external surface. 

 In the early and immature state of the ovaria these trun- 

 cated bases are not produced, and the young ovary has its 

 outer surface bristling with pointed spicula, which are most 

 acute in the youngest specimens, and becoming gradually 

 more obtuse as they approach maturity. After the prolific 

 contents of the adult ovary has been liberated, the internal 

 cavity is gradually filled up by the extension inwards of the 

 apices of the cuneiform spicula until it becomes eventually 

 a solid body ; and a similar secretion of siliceous matter is 

 also frequently continued at the outer surface until it often 

 assumes an irregular tuberous and quite abnormal ap- 

 pearance. 



The ovarian stratum of the crustular dermis is princi- 

 pally composed of exhausted solid ovaria, but occasionally 

 near the outer surface of the stratum a few prolific ones 

 may be observed ; but the greater number of these bodies 

 and of those in an early stage of development, are situated 

 amid the deeply-seated portions of the sponge, scattered 

 irregularly over the sarcodous membranes and deeply im- 

 mersed in the sarcode. In the young state they each 

 appear to be surrounded by a firm stratum of sarcode, 

 which, from its perfectly smooth and circular form, is ap- 

 parently contained within a proper membrane, but in the 

 fully developed and in the exhausted ovaria this sarcodous 

 envelope is not observable. This description of the organi- 

 zation of the genus will apply equally well to any one of 

 the seven species with which I am acquainted, and also to 

 the nearly allied genus Pachymufisvta, excepting the mode 

 of the arrangement of the skeleton in the latter. 



