RKPORT OF EXECUTIVE COMMITTEE. I43 



of the collection. Some remarkable forms were made known. Among 

 such may be mentioned Sderothamnopsis compressa, which resembles 

 in the shrub-like habitus of its stony skeleton the hitherto unique 

 Sderotka?n?i2is clatisii Marsh. 



Light was thrown on the habitat of some of the Hexactinellida 

 living at great depths. Thus Caulophacus was found growing upon 

 the root spicules of Hyalonema. 



Evidence of a convincing character was gained that the complex 

 tubular hexactinellid genera Eurete and Farrea are derived ontoge- 

 netically from simple cup-like forms. 



In several Hexactinellids what may be described as a peculiar hy- 

 pertrophy of the skeleton was obser\'ed. The phenomenon is prob- 

 ably pathological and may indicate an effort of the sponge to shut off 

 one part (diseased?) of the body from the rest. 



Observations were made on several aberrant forms of sponge 

 spicules, with the result that more has been learned as to the phy- 

 logeny of such skeletal elements as the discohexasters and scopulae 

 of Hexactinellids and the protriaenes and asters of Tetractinellids. 



Our knowledge of the character and extent of variation in sponges 

 has been increased by the study of this collection. Cases are recorded 

 in which variation within a species affects not only the body shape, 

 but the general anatomy as well. For instance, in a species of lophon 

 the character of the surface varies conspicuously, owing to divergence 

 in the character of the main canals and the surrounding tissue. 



Among the numerous variation phenomena exhibited by the skel- 

 eton, an excellent case of correlated variation was discovered in a 

 species of the hexactinellid genus Caulophacus . Here the spicules 

 coating the two opposite (pore and oscular) surfaces of the body 

 vary in the same direction, and thus in different individuals the pro- 

 portionate difference between them is preserved. In certain sponges 

 the variation exhibited by the spicules tended toward the condition 

 characteristic of a different though allied .species or subspecies. A 

 striking case was afforded by the new hexactinellid form Farrea occa- 

 claviformis, in which some spicules were found closeh' similar to the 

 highly specialized clavulse characteristic of Farrea convolvulus F. E. 

 Sch. Two cases of a phenomenon were found, which is perhaps to 

 be regarded as a kind of qualitative variation. The phenomenon in 

 question is briefl}^ this : Two sets of individuals living together in 

 the same locality and which are otherwise indistinguishable differ 

 conspicuously in respect to a single point. One case was afforded 

 by the monaxonid sponge lophoyi, the other by the hexactinellid 

 II 



