REPRODUCTION AND ARTIFICIAL PROPAGATION OF FRESH-WATER MUSSELS. 1 75 



It was natural to suppose that the blood of the fish would offer the most favorable 

 nutritive conditions for the development of the glochidia, and hence it has been used in 

 most of the experiments, which, moreover, have been made in the spring, when the water 

 in the laboratory was comparatively warm and the metamorphosis, if it had occurred, 

 would have taken place as rapidly as possible. 



The glochidia of Lampsilis ligamcntina and L. subrosirata were carefully removed 

 from the marsupium with a sterilized pipette and then repeatedly washed in distilled water 

 in order to obtain them as free as possible from bacteria and other organisms. A drop of 

 blood was next taken from a fish's heart and placed on a cover glass and a few glochidia 

 immediately introduced into it. The cover glass was then inverted over a hollow slide 

 containing a moist piece of filter paper, and the chamber sealed with vaseline. Every 

 precaution was taken to avoid contamination by bacteria. As soon as the glochidia 

 came into contact with the blood, of course they snapped shut in the manner already 

 described and in doing so inclosed some of the corpuscles, which it was to be presumed 

 would be ingested by the mantle cells. Although in some cases bacteria and infusoria, 

 probably introduced with the glochidia, appeared, in a majority of the cases the cultures 

 remained free from foreign organisms. In the latter event the glochidia lived for a few 

 days, but finally died without showing any indication of further development. Experi- 

 ments were tried with the blood of the frog and of Necturus, and also with extracts of 

 fish's tissues, bouillon and other nutritive media. In all, however, the results were 

 negative. The failure may possibly have been due to insufficient aeration, and experi- 

 ments are now being devised in which oxygen is to be introduced into the moist chambers, 

 and it is hoped that we shall yet succeed in rearing the glochidia in nutritive media 

 through the metamorphosis. 



VI. POST-LARVAL STAGES. 



BEGINNING OF THE GROWTH PERIOD AND LIFE ON THE BOTTOM. 



The changes occurring during the parasitism and by means of which the glochidium 

 becomes transformed into the young mussel, ready for life on the bottom, are more prop- 

 erly described by the term development than by the word growth. The latter process 

 becomes the conspicuous feature only when the miniature mussel has left the fish. From 

 this time onward there are very few changes to which the term development may be 

 strictly applied; for, with the exception of the outer gill, all the important organs of the 

 animal have been laid down and have assumed something of their definitive structure 

 (fig. 47, pi. XII). 



As soon as they are liberated from the fish the young mussels become quite active 

 and move about on the bottom of a dish by means of the foot (fig. i8, pi. viii, and fig. 48, 

 pi. xii), securing a hold by flattening the ciliated distal end against the bottom, and then 

 drawing up the body after the characteristic fashion of lamellibranchs. In these move- 

 ments the cilia of the foot play an active part ; they beat vigorously while the foot is being 

 extended, and apparently are effective in part at least in causing the protrusion. When 



