1887.] NATURAL SCIENCES OF PHILADELPHIA. 215 



though it rarely attained an inch in tliickuess. One such locality 

 is particularly remembered,-the so-called Corinthian Avenue reser- 

 voir, which had not been emptied for several years ; here the finest 

 specimens might have been gathered, literally "by the bushel," and 

 probably one half that measure was taken away in great slices or 

 "slabs" under my arm. 



These masses were almost certainly the results of many years un- 

 disturbed growth. I have described this species as persistent, to a 

 degree unknown and almost impossible to imagine, in the case of 

 any other North American sponge. The compactness of its skele- 

 ton texture is such, that, except in the event of actual violence, such 

 as the pressure of ice etc., I do not believe that the spicules slough 

 away during the winter, as do most of the others. Its gemmules, 

 therefore, are rarely liberated, and the species in consequence is not 

 largely diffused. 



Transverse sections through the masses alluded to, show an upper 

 or outer layer, about one eighth inch in thickness, of skeleton spic- 

 ules in their normal positions, as formed ; and below them a series 

 of rather irregular lamina, composed almost entirely of gemmules, 

 within their specialized lattice capsules. 



The years of occasional study already given to this species leave 

 several problems yet unanswered ; prominent among which, is that 

 of the order of these serial growths; which I must refer to my more 

 successful followers. My difficulty may be stated thus. Let us sup- 

 pose a sponge of this species, at the end of its first season's growth. 

 It then, undoubtedly, consists of a layer of gemmules, surmounted 

 by a film of skeleton spicules. There is reason to believe that lit- 

 tle of the latter will be washed away during the winter season, but 

 when spring comes, the contents of the gemmules, escaping through 

 their forarainal orifices will probably(?) reclothe the naked skeleton 

 (realizing Ezekiel's vision of the dry bones,) secrete fresh silica and 

 at a slow rate continue the growth of the mass. 



As the next season of hybernation arrives, what must happen? 

 A second layer of gemmules will be deposited ; but where ? It does 

 not appear to be at the summit of the sponge of the first season ; 

 for our section, in that case, would show a regular alternation of 

 gemmules and of skeleton spicules in position. Is the second layer, 

 then, formed above the first of the series of gemmules or below it ? 

 That is, in my fragment, now probably ten or twelve years of age, 

 are the most recent gemmules highest or lowest in the series ? I 



