1921.] N. Annandale & R. B. S. Sewei.i, : Vivipara. 



279 



Part IV.— BIONOMICS.' 

 By R. B. Seymour Sewei<i<. 



The Life-history. 



The breeding season of Vivipara hengalensis, that is to say 

 the period during which the young are born, commences early in 

 the year and seems to extend througliout the whole of the hot- 

 weather and monsoon periods up to and probably bej^ond vSeptem- 

 ber ; but tlie period of most intense reproduction is from April 



5 10 15 20 



Fig. 20. — Length measurements of 35 examples of young \'ivipara bengalensis, 

 born in experimental tanks, at the age of 3 months old. 



to July. During this period the uterus of a mature female is 

 crammed with eggs, containing j'oung in var5'ing stages of deve- 

 lopment, but young Viviparidae are to be found i>i titero at all 

 seasons of the year. I have even found them to be present in 

 examples that had buried themselves in the mud at the bottom 

 of a tank in Lahore at the onset of the cold weather and were dug 

 up in December. Examples of Lecythoconcha lecythis, dug from 



' In compiling this section I am greatly indebted to Dr. .Annandale for 

 many additional notes and observations. 



