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 1891, by which time my observations were finished. Real- 
izing that the completed paper would be slow in appearing, I 
published in the JourNAL oF Morpuo.ocy (Vol. V, No. 3, 
1891) a brief account of the more important results. 
UNIVERSITY OF NORTH CAROLINA. 
I. ApuLT STRUCTURE AND GEMMULE DEVELOPMENT OF 
ESPERELLA FIBREXILIS, N. SP. 
1. 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. 1. 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. LEsperella fibrexilis, n. 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. 
