Howe : Pmvcological studies 499 



exception longer tlian broad. The very different utricles of the 

 subcortical layer, with other characters, well distinguish //. ciincata 

 from H. discoidca and we think it clearly entitled to specific rank. 

 In any event, if one's conception of specific limitations should 

 prove sufficiently elastic to include the two under one specific 

 name, Decaisne's Ilalhncda discoidca has the right of way on 

 priority grounds. 



The older writers on the species of Haliuicda gave very little 

 attention to histological characters. Kiitzing,* indeed, remarked 

 upon the uniformity of their structure and considered it unneces- 

 sary to give detailed figures illustrating the anatomy of each 

 species. Professor Askenasy f in 1888 made an important advance 

 in describing and figuring the details of structure and in empha- 

 sizing their value in distinguishing species, but he apparently did 

 not examine authentic material of certain species described by his 

 predecessors, and thus quite naturally made a wrong application 

 of some of the specific names. Mrs. Gepp (Miss Ethel Sarel 

 Barton) in preparing her monograph of "The Genus Hahmeda " 

 (/. <r.) recognized fully the importance of seeing original materials 

 and rendered an important service by investigating carefully the 

 characters of the nodal filaments of the central strand and insisting 

 on the value of these characters in diagnosing species, but she did 

 not emphasize sufficiently the characters of the peripheral utricles 

 and the utricles of the subcortical layer, parts which, in most 

 species, at least, offer peculiarities of as much constancy and value 

 as do the nodal filaments. That the nodal filaments are not 

 altogether invariable is seen in Halimeda discoidca, where fusions 

 of the H. Tuna type and of the //. Opiuitia type sometimes occur 

 side by side in a single node (figures 19 and 20) and also in H. 

 Moni/e, in which rarely the filaments are only superficially cohe- 

 rent. The peripheral utricles and those of the subcortical layer 

 also have, of course, a certain range of variation in each species ; 

 nevertheless that range is limited and these elements possess char- 

 acters oftaxonomic value of which any final and complete system 

 of classification must take cognizance. 



The specimens from Bermuda, Porto Rico, and Jamaica, which 



*Tab. Phyc. 7 : 9. 1857. 



t Forschungsreise S.M.S. Gazelle 4 : 11-14. //. j, 4- 



