260 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



The specimeus were prepared by the Tullberg ('91) method, which 

 consists in stupefaction by the gradual introduction of magnesic sulphate 

 into the water containing the actinians, and in subsequent hardening by 

 means of chromic acid. This method, when properly employed, yields 

 beautifully expanded and thoroughly hardened specimeus, and my expe- 

 rience with it has been such that I can fully indorse the recommendations 

 given it by Tullberg ('91), Carlgi-en ('93, p. 7), and others. Speci- 

 mens prepared in this way were cut transversely with a common razor, 

 and the number and arrangement of the mesenteries and siphonoglyphs ^ 

 were recorded. Owing to the large size of the specimens, this could be 

 easily done under the magnification of an ordinary hand lens. 



Siphonoglyphs. — The Hexactinia, to which iletridium belongs, were 

 until recently supposed to possess always two sij^honoglyphs : but this 

 surmise has been shown to be not well grounded, and, in the species 

 under consideration, as McMurrich ('91, p. 131) has already pointed 

 out, either one or two siphonoglyphs may be present. In the 131 

 specimens that I examined, 77 (or about 59 per cent) had only one 

 siphonoglyph (Fig. 3), 53 (or about 41 per cent) had tioo siphonoglyphs 

 (Fig. 1), and a single specimen possessed tliree such organs (Fig. 6). In 

 no instance was a specimen found without a siphonoglyph. The smooth 

 surface of the siphonoglyph is so strongh" contrasted with the longitu- 

 dinally ribbed surface of the rest of the oesophagus that in none of the 

 specimens examined was there any iincertainty as to the number of 

 siphonoglyphs present. The striking difference between these two kinds 

 of sui-face cannot be made to appear so clearly in the figures as it did 

 in the actual specimen, where, in addition to the cut face, the natural face 

 of the oesophagus could also be inspected. McMurrich ('91, p. 131) 

 remarks that in the individuals examined by him, those with one sipho- 

 noglyph were almost, if not quite, as frequent in occurrence as those 

 with two, but in my enumeration it will be seen that they were really 

 somewhat more numerous. 



Since only one of the 131 specimens possessed three siphonoglyphs, it 



1 The term " siphonoglvphe " was first introduced into zoological nomenclature 

 by Hickson ('84, p. 694), and has since been widely accepted. Professor Hickson 

 kindly informs me that the last syllable of this term is derived from the Greek 

 word y\v(pis, which in the plural form, y\v(piS€s, has been used to signify the grooves 

 on an arrow for the insertion of the feathers. The root of this word appears to 

 call for no final e, and since in making English words it is best, as Professor 

 Hickson remarks, to use only roots, I therefore propose to change the spelling 

 of the term in question by omitting the final e, and to this Professor Hickson 

 assents. 



