Mr. H. J. Carter on the Suhspherous Sponges. 11 



Before the particles reach the pores, they pass through 

 apertures in a delicate expansion of sarcode which, mem- 

 brane-like, covers the Spongillay which apertures (about 

 l-700th of an inch in diameter) are extemporized here and 

 there in this expansion, or closed, as occasion may require. 

 Again, the single oscule, which is supported on a tubular 

 mammillary projection and passes through the sarcodal expan- 

 sion, can also be closed or opened as required by the sponge. 



But these apertures are situated in a substance which is too 

 delicate and evanescent to last long under rough treatment ; 

 and hence the term " pores " has been used by naturalists for 

 those superficial cavities which this sarcodal expansion covers 

 in the more solid and durable parts of the sponge, viz. those 

 which are evident to the unassisted eye. Hence the name 

 " Porifera " applied to the class by Dr. Grant, the term 

 " oscule " having only been used for the larger pore which is the 

 opening of the excretory system of canals. " Vent " has also 

 been applied to the latter, which, as regards function, is, of 

 course, more suitable. 



Thus Dr. Johnston, in his ' British Sponges,' p. 196, de- 

 scribes the surface of Geodia zetlandica as " dimpled in some 

 places, with numerous pores placed pretty closely together, 

 and large enough to be visible with the naked eye," — to 

 which Dr. Bowerbank (Brit. Sponges, vol. ii. p. 46) objects, 

 stating that " These orifices are not the pores, but they are the 

 intermarginal cavities which receive the minute streams from 

 numerous pores situated immediately above and within a short 

 distance of them ; the true pores, perforating the dermal mem- 

 brane, are too minute to be visible without the assistance of 

 considerable microscopic power." Yet, in describing Pachy- 

 mntisma^ only seven pages further on (p. 53), the same author 

 states : — " In the living condition the pores are not visible to 

 the unassisted eye, but in the dried state they are very dis- 

 tinctly seen;" while at p. 110 of vol. i. we read: — "In Pa- 

 chymatisma Johnstonia^ Bowerbank, a British sponge closely 

 allied to the genus Geodia^ we find the dermal membrane 

 perforated by innumerable pores, some as minute as -roW iiich 

 in diameter, while others attained the size of -^-^ inch." 



It is not difficult to see that there is some confusion here : 

 viz. that in the latter quotation " pores " (ranging from 



to -g-l^ inch in diameter), which certainly cannot be distinctly 

 seen by the unassisted eye, are stated in the former quotation, 

 although not visible to "the unassisted eye" in the living 

 condition, to be " very distinctly" so in the dried state. 



In this dilemma I prefer the prescriptive meaning given to 

 the pores by Dr. Johnston, and as such shall continue to apply 



