153 



PLATE LX. 



SPONGILLA LACUSTRIS, Johnston. 



Vol. ii, p. 342, ' Mon. Brit. Spongiadse.' 



Fig. 1. Represents a specimen obtained from the 

 Thames at Cookham, where such complex masses of 

 the sponge are by no means uncommon. Natural size. 

 Dried state. 



Fig. 2. A simple branching specimen from the same 

 locality. Natural size. Dried state. 



Fig. 3. A skeleton spiculum. X 250 linear. 



Fig. 4. One of the fusiformi-acerate, entirely 

 spined, tension spicula, from the dermal membrane. 

 X 250 linear. Another of these spicula, X 660, is 

 represented by fig. 90, Plate IV, vol. i, ' Mon. Brit. 

 Spongiadse.' 



Fig. 5. Three of the subarcuate, acerate, entirely 

 spined spicula from the envelope of the ovary of this 

 species, showing the great variations in form to which 

 they are subject. X 250 linear. Another of these 

 spicula is represented by fig. 203, Plate IX, vol. i, 

 ' Mon. Brit. SpongiadaD. 5 X 660 linear. 



Fig. 320, Plate XXII, in the same volume, repre- 

 sents an ovarium of 8. lacustris, prepared by nitric 

 acid so as to exhibit these spicula in situ. X 183 

 linear. 



