4 GLOCHIDIA OF FRESHWATER MUSSELS. 



In order to secure uniform results uniformity in the preparation of 

 the material is of the first importance. The method of procedure, 

 therefore, briefly stated, was throughout as follows: A section of the 

 mussel gill, if large, or the entire gill, if small, is first carefully removed 

 and killed in 10 per cent formalin, in which it is allowed to remain a 

 few hours. The section is then carried through alcohols of increasing 

 strength up to 70 per cent, when the glochidia are teased out and 

 stained in eosin or cochineal, the latter stam being the most satis- 

 factory in most cases, after which hardenmg is carried slowly up to 

 95 per cent alcohol. Oil of cloves has proved to be the most satis- 

 factoiy clearing agent, xylol being too violent in its action. Mounts 

 are made in Canada balsam. The same method has been pursued in 

 preparation of fish gills bearing natural infection in order to produce 

 uniform results. This method gives preparations of glochidia in 

 which the valves of the shell are closed, but if they are desired ex- 

 panded, then the method used by Lefevre and Curtis " is recom- 

 mended of slowly introducmg crystals of cocaine or chloral hydrate 

 into a watch glass containing the larvae. 



It is not desirable to go into detail in the description of the 

 glochidium, as it is believed reference to the analytical key and the 

 figures themselves will do more to make the differences apparent 

 than pages of descriptive matter. The importance of the glochid- 

 ium in the classification of the Unionidse is recognized, but to try to 

 show the relationship of the different genera and species at this time 

 with our present lack of material would be unsafe, to say the least. 

 At the present time it will be best to call the reader's attention to a 

 few important points only. 



It has been ascertained that variation in size is comparatively 

 slight in a given species, except in one instance, where some glochidia 

 of L. luteola from Clear Lake, Iowa, were found to be uniformly 

 smaller than those of the same species taken in the Cedar Kiver, 

 but, as the adult shells from this lake are very small and thin-shelled 

 as compared with those from the Cedar River, the difference in size of 

 the larval mussel may be correlated. There was, however, in this case 

 no apparent difference in the shape or proportions of the glochidia 

 from the two sources. 



Drawings have been made of what might be safely considered as 

 typical specimens, except in the case of Cyprogenia irrorata (fig. 11, 

 pi. i) and Quadrula Jieros (fig. 32, pi. ii), where the only material 

 available was not quite mature, although advanced sufficiently in 

 development to give a most excellent idea of the subsequent shape 

 and size. 



« studies on the reproduction and artificial propagation of freshwater mussels. By George Lefevre 

 and Winterton C. Curtis. Bulletin Bureau of Fisheries, ^ ol. xxx, p. 150. 



