28o 



Records of the Indian Museum. [Vol. XXII, 



dried mud at the edge of a swamp in Manipur, and l^irought to 

 Calcutta in March, produced living young when placed in water. 



Newl}^ born examples of V. bengalensis are comparatively 

 well-developed and already show 3A turns of the spiral in the shell. 

 In a preceding part of this paper Dr. Annandale has described the 

 3'oung shell. 



mm 



36 H 



34 



33 



32 



31 



30 — 



29 



28 



27 



26 



25 



24 - 



23 - 



22 - 



21 



20 



19 



18 

 17 

 16 

 15 

 14 

 13 

 12 

 11 

 10- 



9 



8 



7 



6 



5 



4 



3 



2 



1 



1918 brood 



1919 brood 



1920 brood 



•••• 

 • •• 



5 10 15 20 25 30 35 40 45 50 



Fig. 21. — Length measuremenis of 409 examples of Vivipara bengalensis, taken 

 from the tank in the Indian Museum compound, July 26tli to .\ugust 2nd, 

 1920. 



Growth at first proceeds rapidly. Newly born individuals 

 measure approximately 3 mm. in maximum height from the apex 

 of the shell to the margin of the peristome, but in less than 

 three months a complete extra whorl has been added and the 

 height of the shell is now approximately 15 mm. During May 

 and August, 1919 a number of examples of Vivipara bengalensis 

 were kept under observation in experimental tanks in the Indian 

 Museum. These adults were introduced into the tanks between 

 the 2nd and 23rd of May, 1919. Young were deposited in large 



