REPRODUCTION AND ARTIFICIAL PROPAGATION OF FRESH- WATER MUSSELS. l8l 



June 29, 1908. November 15, 1910. 



Lampsilis veniricosa: 



(i) 45 by 30 mm., 16 grams 85 by 65 mm., 129.85 grams. 



(2) 47 by 32 mm., 15 grams 81 by 57 mm., 115.5 grams. 



(3) 47 by 30 mm., 16.5 grams 96 by 67 mm., 145.2 grams. 



Obovaria ellipsis: 



(i) 52 by 52 mm., 59.1 grams 57 by 55 mm., 74.6 grams. 



(The identification of this specimen is somewhat uncertain.) 

 Quadrula solida: 



(i) 35 by 36 mm., 27 grams 45 by 46 mm., 46.3 grams. 



Anodonta imbecillis: 



(i) 30 by 25 mm., 8 grams., 61 by 28 mm., 13.3 grams. 



In each case, the first measurement is the greatest antero-posterior length of the 

 shell, and the second the distance from the top of the umbo to the ventral margin taken 

 approximately at right angles to the lines of growth. An interesting and important fea- 

 ture of these specimens is the fact that the original margin is clearly indicated by a con- 

 spicuous line on the shell of each, and as the measurements within this line correspond 

 with the original measurements, the identification is made sure for each individual. 



We quote below an analysis of the results sent us by Dr. Coker.who made the second 

 series of measurements after the recovery of the cages: 



Lampsilis -ventricosa. — They have increased in length by 34 to 39 mm. and in height by 25 to 37 

 mm., and they now weigh approximately 7, 8 and 9 times as much, respectively, as when first put out. 

 Furthermore, the added area of shell is divided by a conspicuous dark ring and a less distinct ring which, 

 one is tempted to assume, represent the periods of cessation of growth during the two winters. If 

 such an interpretation is made, the growth was accomplished chiefly during 1908 and 1909, while during 

 the present year (1910), the mussel having reached adult size, the growth has been considerably less. 



Increase in size stated by percentage (present measurements compared with original measurements). 

 Period, June 29, 1908, to November 15, 1910, 2 years, 4^ months: 



Length. Hcielit. Weight, 



Specimen no. I per cent.. 188 217 812 



Specimen no. 2 do.. .172 178 770 



Specimen no. 3 do. . . . 204 223 880 



The proportion of increase is slightly greater in height than in length, and the coefficient of increase 

 in weight is, as might be expected, something like the cube of the coefficient of increase in either 

 dimension. 



Obovaria ellipsis. — The specimen has probably gained very little in length or height but materially 

 in weight. It was nearer its adult size, is doubtless a slower growing species, and has probably gained 

 in weight by increase of thickness of shell. But we are not so sure of the identity of this specimen. 



Quadrula solida. — Has gained nearly 30 per cent in length and height and 70 per cent in w^eight. 



Anodonta imbecillis. — Has more tlian doubled in length, with negligible increase in height, while 

 it has increased 66 per cent in weight. This is particularly interesting as showing a marked change 

 in form from the young to the adult. 



Text figure 4, a and b, represents outline sketches of two of the three specimens 

 of L. ventricosa described above, showing the exact size of each after the completion of 

 the growth in the fall of 1910; the line marked a is the margin of the shell at the time the 

 planting was made in 1908; while lines /) and c are the two successive rings indicating 

 cessation of growth. The two areas inclosed between these lines, representing the two 

 chief periods of growth which have occurred, are not of equal extent in the three speci- 



