252 McMURRICH. [Vol. II. 



I. Historical. 



Before considering the literature which refers especially to 

 the filaments of the Zoanthidae, a brief review of the literature 

 of the hexactinian filaments seems advisable, since it is in this 

 group that the filaments have been most thoroughly studied. 



Of the structures usually grouped together as parts of a mesen- 

 terial filament, the acontia, which are extruded from the body 

 by the Sagartiadae, were naturally the first observed, having 

 been described by Dicquemare in 1775, and, according to Con- 

 tarini, by Gesner as far back as 1558. The first description of 

 the filament proper of which I am aware was by Spix ('09),^ but 

 from his time onward frequent references to them occur. The 

 older authors knew only that portion of the filament which we 

 now term the glandular streak (Nesseldriisenstreif), and they 

 regarded this as a coiled tube occupying the free edge of the 

 mesentery. The supposed tubular character of this structure 

 led it to be considered either as a reproductive organ or a repro- 

 ductive duct, a view to which Teale ('37) was the first to take 

 exception. He, believing with Rapp ('29) that testes did not 

 occur in the Actiniae, and that the ova developed without fer- 

 tilization, and were rather "germ granules" or "gemmiferous 

 bodies " than true ova, and recognizing that the filaments were 

 not oviducts, suggested that they might be analogous to the 

 salivary, pancreatic, and hepatic follicles of higher animals. 

 Erdl ('42), by the discovery of testes, disproved the opinions 

 of Teale and Rapp with regard to the organs of reproduction, 

 but he, too, suggested a possibly hepatic function for the 

 filaments. 



The underlying idea of these suggestions of Teale and Erdl 

 that the filaments were concerned in the digestive processes 

 gained in popularity as new observations were added, while at 

 the same time their direct homology with liver, pancreas, or sali- 

 vary glands became more improbable. Without reviewing the 

 various theories as to their function at greater length, it may 



1 I have not been able to consult the paper of Spix and know it only by a 

 quotation given by Teale ('37). 



