No. 3-] DEVELOPMENT OF MARINE SPONGES. 279 



to be made in the future in the direction of the cultivation of 

 useful sponges would be greatly aided by a knowledge of the 

 life-histories of sponges in general, approved of my wish to 

 continue the investigation, which was made the more attractive 

 by the discovery in a sponge, ^ common about Woods Holl, 

 Mass., of gemmules essentially like those I had already found 

 in a Bahama form. The work was accordingly carried on in 

 the Fish Commission Laboratory at Woods Holl until the fall 

 of 1 89 1, by which time my observations were finished. Real- 

 izing that the completed paper would be slow in appearing, I 

 published in the Journal of Morphology (Vol. V, No. 3, 

 1 891) a brief account of the more important results. 



University of North Carolin.\. 



I. Adult Structure and Gemmule Development of 



ESPERELLA FIBREXILIS, N. SP. 



I. Adult. 



Esperella fibrexilis is small, the masses usually having a 

 greatest diameter of 4 or 5 inches. It may assume any shape, 

 sometimes appearing as a flat incrustation, and again as a 

 spheroidal mass. Quite commonly its upper surface forms 

 conical processes, often acute and very ragged. And with 

 these there may be combined irregular ridges with sharply cut 

 edges, as in the sponge shown in Fig. i. It is rare to find this 

 sponge moderately clean, it being nearly always covered with 

 hydroids, polyzoa, and especially a cylindrical alga, all of which 

 are firmly rooted in the body. The feeble development of the 

 skeleton more than anything else marks it off from the known 

 members of this genus. 



Diagnosis. Espc7'cUa fibrcxilis, u. sp. — Sponge amorphous, 

 yellowish-brown, and of slight consistency. Dermal membrane 

 containing no spicules or almost none, everywhere separated 

 from subjacent tissues by subdermal cavities, and everywhere 



1 For calling my attention to this interesting sponge (Esperella fibrexilis) I am 

 indebted to Prof. T. H. Morgan. 



