1863.] DR. J. S. BOWERBANK ON THE SPONGILLID.E. 471 



1856, he writes, "I forgot to mention that Spongilla grows abun- 

 dantly in the water-pipes by which the city of Boston is supphed 

 with water from a small lake. I think it must materially diminish 

 the water-way in the pipes, and probably be connected with the bad 

 taste which the water has in seasons of great drought." With the 

 latter part of these observations especially I am strongly inclined to 

 concur, as I have always observed that a small portion of either of 

 our European species rapidly deteriorated a comparatively large body 

 of water to such an extent as to render it unfit to sustain either its 

 own life or that of any other animals of higher organization. The 

 encouragement of Confervce in tanks supplied with such water would 

 probably help to correct the deleterious effects of the Spongilla. 



EXPLANATION OF PLATE XXXVIII. 



Fig. 1. Spongilla Jlwviatilis. — a. A spiculum of the skeleton, X 108 linear. 

 b. A birotulate spiculum of the ovaria, x660 linear, c. A view of 

 the external surface of a rotula, X660 linear. 



2. S. Leidii. — a. A spiculum of the skeleton, X 108. h. A birotulate spi- 



culum of the ovaria, X 660. 



3. S. Capewelli. — a. A spiculum of the skeleton, X 108. 6. A birotulate 



spiculum of the ovaria, X 660. c. A view of the external surface of a 

 rotula, X660. 



4. S. Meyeni. — a. A spicuhxm of the skeleton, X 108. h. A birotulate spi- 



culum of the ovaria, X 660. 



5. S.plumosa. — a. A spiculum of the skeleton, Xl08. h. A bu-otulate spi- 



culum of the ovaria, X 660. c. A view of the internal surface of a 

 rotula, x660. d. An elongate pileated spiculum, an early condition 

 of the subsphero-steUate form, x400. e. A fully developed multi- 

 radiate, subsphero-stellate, pileated spiculmn of the sarcode, X 400. 



6. S. Baileyi. — a. A spiculum of the skeleton, X 108. I. A birotulate spi- 



culum of the ovaria, X 660. c. One of the tension-spicula of the mem- 

 branes, X660. 



7. S. gregaria. — a. A spiculum of the skeleton, X 108. h. One of the spi- 



cula of the case of an ovarium, without spines, Xl08. c. A spiculum 

 of the case of an ovarium, abundantly spinous, Xl08. d. A side view 

 of one of the birotulate spicula of an ovary, X 1100. e. A view of the 

 external surface of a rotiila, X 1100. 



8. S. paulula. — a. A spiculum of the skeleton, X 108. h. One of the inequi- 



birotulate spicula of the ovaria, X 660. 



9. S. retienlata. — a. A spiculum of the skeleton, Xl08. h. A boletiform 



spiculum of the ovaria, X 660. 



10. S. recurvata. — a. A spiculum of the skeleton, Xl08. h. A slender bo- 



letiform spiculum of the ovaria, X 660. c. A multihamate, birotulate 

 spiculum from the ovaria of the same Sponge, X 660. 



11. S. Brotonii. — a. A spiculum of the skeleton, X 108. h. One of the spi- 



cula of the reticular case of an ovarium, X 108. c. An umbonato-scu- 

 tulate spiculum of the ovaria, showing the external surface, x660. 

 d. A side view of one of the same form of spiculum represented by 

 fig. c, X660. 



12. S.Batesii. — a. A spiculum of the skeleton, Xl08. h. An entirely spined 



fusiformi-acerate spiculum from the outer surface of an ovarium, 

 X 660. c. One of the umbonato-scutulate spicula from the inner por- 

 tion of the wall of an ovarium, X 660. 



13. S. corallioides. — A spiculum of the skeleton, X 108. 



14. S. lacustris. — a. A spiculum of the skeleton, X 108. b. A fiisiformi- 



