274 BULLETIN" 100, UNITED STATES NATIONAL MUSEUM. 



of classification which splits genera into subgenera and species into 

 subspecies, with the tacit understanding that there must be a sub- 

 group into which each individual organism will fit. However for- 

 eign such a mode of classification is in the abstract to our ideas on 

 the evolution of organisms, it is clear that in the actual work of 

 classification it has to-day a considerable influence. 



As to technical methods I can refer those who are not already 

 familiar with such to a previous statement (Wilson, 1902, p. 378). 

 I may add that for sections celloidin imbedding proves very con- 

 venient. Surface preparations of dermal and cloacal membranes 

 are desirable. For boiling out spicules many prefer nitric acid to 

 caustic potash. In the study of lithistid desmas the nitric acid is to 

 be followed by hydrofluoric acid (Solhis 1888, p. clxv). I maj r 

 add that the crepis of the desma is sometimes more distinct in water 

 than in balsam; I have also used to advantage pure glycerine and, 

 again, cedar oil. 



The customary methods are employed with respect to spicule 

 measurements — that is, the aim is always to give an idea as to the 

 characteristic size, namely, the common average, young forms and 

 extremes being excluded. For this purpose sometimes the dimen- 

 sions of selected representative spicules are given; sometimes an 

 average is given covering a number of spicules of commonly occur- 

 ring sizes. More often, perhaps, the common range of size, common 

 minimum to common maximum, is given. With this understanding 

 the qualifying word " about " has been usualh r omitted. 



There is a minor linguistic matter in which English-writing 

 zoologists should, it seems to me, reach an agreement. I refer to the 

 formation of plurals in the case of words like desma, dragma, sigma, 

 toxa (some of the dictionaries give toxon, but it is the made-over 

 form, toxa, that has come into actual use in the literature, following 

 Sollas, not the Greek singular), oxea, chela, etc. We use such words 

 in the singular as English words and there is no valid linguistic 

 reason for not following Sollas* example (1888, ,p. lix) in using the 

 "s" plural. Where the word has preserved its Latin form (as 

 chela) we especially shrink from this plural, but I realize that if the 

 terms are to be used freely by many, as should be the case, we must 

 use them as English words and as we now say museums, so must Ave 

 learn to say aquariums and chelas. In this reform spirit I have 

 gone over my text and endeavored to bring it throughout into con- 

 formity with Sollas* principle. The singular forms clad, rhabd, 

 which demand the "s" plural, are used instead of the Latin forms, 

 clad us, rhabdus, etc. 



Dendy 1 (1921, p. 101) takes particular exception to the use of 

 oxea in the singular as " erroneous " and would use oxeon, plural 



1 The death of this eminent investigator, to whom we owe so much, was announced 

 while this paper was passing through the press. 



