THE NAUTILUS. 17 



glochidia remain in this helpless situation until they die, un- 

 less they happen to come in contact with the host on which 

 they pass through the post-embryonic development as para- 

 sites." The same statement occurs in the "Studies on the 

 Reproduction and Artificial Propagation of Freshwater Mus- 

 sels" by the same authors in the Bulletin of the U. S. Bureau 

 of Fisheries, Vol. XXX (Document No. 756, page 152). 



The occurrence of glochidia in plankton is noted and com- 

 mented on in some fullness of detail by Kofoid in his report 

 on the Plankton of the Illinois River, Part 2, page 287, where, 

 under the heading "Lamellibranchiata" he remarks: "This 

 group is represented in the plankton by the larval stages or 

 glochidia of the Unionid<r, which form an important part of 

 the bottom fauna of the stream and its tributaries." Among 

 those mentioned as occurring in the plankton are Anodonta 

 corpulcnta Cooper, glochidia "referred with some uncer- 

 tainty" to Lampsilis anodontoides, and glochidia presumably 

 belonging to Arcidens confragosus. 



Kofoid 's remarks concerning the abundance, numbers and 

 percentage of occurrence, temperature relations and seasonal 

 distribution, as well as his remarks on identification of the 

 glochidia encountered, preceding as it does the strenuous 

 attempts at description and identification of glochidia and 

 ascertainment of breeding seasons of different species of mus- 

 sels later entered into with such avidity in behalf of mussel 

 propagation, form one of the most fascinating episodes in 

 scientific research. His discussion is unfortunately too long 

 to quote in a brief article like that intended here, but too 

 interestingly precious to be missed by anyone studying the 

 history of mussel propagation. 



Peremptorily dismissing the temptation to quote remarks 

 illuminating other but what would anciently be called imper- 

 tinent phases of the subject here, it only remains to remark 

 that what is really the one pertinent query, that of the rela- 

 tion of the glochidia to the surface, is left in doubt. The 

 wording of the one introductory sentence quoted, doubtless 

 perfectly clear when written, develops an ambiguity which 

 increases with a growing interest in glochidia rather than 



