A Stiidij of the Parasites of the UnionkUc. 407 



individuals of Lainpsilis Ugamentimis ; and (3) within the 

 ovary of a single specimen of LainpsUis ventrieosns. These 

 are evidently all immature forms, the clam serving them only 

 as an intermediate host. 



Bucephalus polijinor]>hits von Baer and two other cercaria 

 forms were found within the viscera of the host. These 

 usually occurred in such ahundance as to obliterate totally 

 the normal tissue of the sexual glands, rendering the whole 

 abdomen as granular as fish roe, or fibrous with the sporo- 

 cysts of the Bucephalus. Extensive infestation with the 

 latter parasite also involves the nephridia, which may be 

 much swollen, their ducts being nearly obliterated by the 

 tangled fibers of sporocysts. This unsexing of the host, and 

 the accompanying changes in the form of the shell have 

 .already been referred to. 



Various species of Atax are common ectoparasites of the 

 Unionidce. Their favorite situations are upon the body 

 surfaces, between the gills or between the gills and abdomen, 

 between the labial palps, or among the papillse fringing the 

 mantle edges at the inhalent siphon. Their eggs are laid 

 either in the body wall, the gills, or the mantle. 



Dr. Eobert H. Wolcott, to whom a part of the Atax 

 material collected in the course of this study was sent, kindly 

 furnished the determinations of the species of this genus 

 included in the following table, which indicates the host 

 species from which these ditt'erent parasites were derived, 

 and also the total number of individuals of each species of 

 Atax found in a given host species. 



Conchophth'irus Jiirtus Ehrbg. and (', anodoiitie Ehrbg., 

 ciliated Infusoria, inhabit the slime investing the body sur- 

 faces. In the accompanying tables no attempt is made to 

 separate the two species. 



CJuetof/astcr limucei von Baer, an oligochsete, is also found in 

 the slime of the various surfaces and in the kidneys. 



The frequent presence of leeches and planarians upon the 

 shell and on the mantle edges, at times indeed within the 

 branchial chamber, was regarded as accidental, and they are 

 consequently not included in the accompanying tabulations. 



