THE SPONGES 



7 





Pacific. Some of the Hexactinellids from great depths have been found to 

 live clustering upon one another: Caidophacits, pp. 39, 46, attached to root 

 spicules of Hyalonema ; Bathydorus, p. 47, attached to root spicules of Hya- 

 lonema and to stalks of Caulophacns or similar sponge. 



Morph 



Further evidence of a convincing character has 



been gained that the complex Earete and Farrea colonies are derived onto- 

 genetically from simple cup-like forms, pp. 60, 61, 66. The close simi- 



larity between the main afferent and efferent canals and their apertures in 

 Poecittastra tricomis is worthy of remark, p. 97. The observations of 



Sollas and of Dendy on the occurrence of a peculiar fenestrated membrane 

 (Sollas's membrane) in the flagellated chambers of certain sponges have 

 been confirmed for two Tetractinellid genera, Poecillastra and P enures, pp. 



99, 103, 109. 



Pathological phenomena in general. In Euplectella skeletal septa of a 

 reticular character have been found crossing the cavity of the sponge, 



p. 29 



In Chonelasma similar septa have been observed, p. 70. 



Ilexactinella 



Weltn 



In some cases 



such masses form layers separating one part of the sponge from another. 

 Possibly all these phenomena are pathological and similar, in so far 



as they may indicate an effort of the sponge to shut off one part (diseased?) 



of the body from the rest. 



Morphology of spicules — variations and "pathological" conditions. In Ilya- 



4 



lonema pateriferum, pathological amphidiscs such as have been observed by 

 Marshall and Meyer and P. E. Schulze occur. In these spicules, p. 28, 



several additional rays of the hexact are developed. Certain details in 



the structure of the discohexasters of Caidophacus sehukei suggest that a 



arise from a hexact through the development of lateral 



hexaster may 



branches on the hexact rays, pp. 44, 45. 



Another case is afforded by 



Ilexactinella labyrinthica of what seems to be the degeneration of an uncinate 



into an oxydiact, p. 77. 



In scopulae present in Sclerothamnopsis com- 



prcssa, the arrangement of the axial canals indicates that the spicule is 

 equivalent to a branched diact, as Schulze has supposed, p. 82. Abun- 



dant transitional forms indicate that the protriaenes of Thenea are modi- 



fied dichotriaenes, p. 85. 



In Thenea piriformis a type of metaster is 



common which may be interpreted as transitional between spirasters and 



euasters, p. 96. 



In Penares foliaformis peculiar dichotriaenes are found 



