118 Mr. C. C. Nutting on the 



Fig. 13. Pinnate papilla from the scale of Sigalion squamatum, Delle 



Chiaje. x 150. 

 Fig. 14. Pinnate papilla from the edge of the scale of Sigalion Mathilda, 



Aud. & Ed. x 200. 

 Fig. 15. Pinnate papilla from the scale of Sigalion (?) Buskii, Mel. 



X loO diam. 



XVI. — The Sarcostyles of the Plumularida?. 

 By C. C. Nutting *. 



There is no little confusion regarding the nomenclature 

 involved in morphological discussions concerning the Hydroida, 

 and nowhere is this fact more evident than in connexion with 

 certain interesting structures found in the Plumularidas and 

 variously called nematophores, protoplasmic processes, defen- 

 sive zooids, sarcodal processes, Machopolyps, "Wehrthiere," 

 and Nesselpolypen by the numerous writers who have investi- 

 gated them. The first mention that I have been able to find 

 of these structures is by Busk in Hunterian Lectures (MSS.), 

 London, 1857, who called them " Nematophores " — a name 

 subsequently used by various writers. Hincks afterwards 

 applied the name " sarcotheca " to the chitinous receptacle, 

 and "sarcostyle" to the sarcodal contents, or rather defensive 

 persons, inclosed within it. Without further discussion on 

 this point, I will state that I use the word nematophore for 

 the receptacle without necessary reference to its contents, and 

 sarcostyle for the organ or person within, and it is to the 

 latter that I invite attention at present. 



The hydroids have been carefully studied by so few zoolo- 

 gists that it may not be amiss to define the sarcostyle more 

 explicitly before discussing it. A careful investigation of any 

 plumularian hydroid will disclose the fact that, beside the 

 hydrothecas containing the hydroid polyps or hydranths, there 

 are numerous usually minute chitinous cups containing an 

 exceedingly interesting structure, which in life is characterized 

 by amazing extensibility. Allman, in 1864, described it as 

 " a soft granular mass which could send forth very extensible 

 processes capable of being greatly protruded, and then so 

 completely retracted as to apparently disappear. These pro- 

 cesses have the power of sending forth pseudopodia, as does 

 the amoeba, and act in many respects as do certain rhizopods." 



* From ' The American Naturalist,' April 1898, pp. 223-230. Read 

 before Section F at the Detroit meeting of the American Association for 

 the Advancement of Science. 



