REPRODUCTION AND ARTIFICIAL PROPAGATION OP FRESH -WATER MUSSELS. 183 



small individual of Lampsilis ventricosa was found alive and active in the sand of the 

 same tank. There can be no 

 doubt that it was derived 

 from the infection referred 

 to, as no young clams of this 

 species had ever been in the 

 laboratory, and no subse- 

 quent infections were made 

 in that tank. The exact size 

 of this young mussel was 41 

 by 30 mm. on December 26, 

 1910. It is still alive, but as 

 late as June, 191 1, it was 

 practically of the same size. 

 Since it is over two years old, 

 it is evident that it is quite a 

 dwarf, and, had it been reared 

 under favorable conditions, 

 it undoubtedly would have 

 been much larger by this time. 

 The tank in which it has 

 spent all of its life is supplied 

 with tap water, which is 

 obtained from deep wells and 

 contains little that a mussel 

 could utUize as food, and its 

 small size is undoubtedly due 

 to the fact that it has been 

 underfed from the beginning. 

 The shell shows no indication 

 whatever of lines of inter- 

 rupted growth, but this is 

 only what might have been 

 expected, as the mussel has 

 never been exposed to low 

 temperatures. It is evident^ 

 therefore, that it has been 

 growing continuously, but 

 very slowly, throughout its 

 entire life. 



This individual, however, 

 is of no little interest, as it is 

 the first fresh-water mussel actually reared artificially from the glochidium, and in a sense 



Fig. 4. — Two individuals of Lampsilis ventricosa recovered on November 15, igio, 

 after having been confined in a wire cage in the Mississippi River for two 

 years and four and a half months. The line a is the original margin of the 

 shell at the time of planting. June 29. 190S, and the lines 6 and c represent the 

 " rings" which are due to the periods of cessation of growth. Natural size. 



