OF COCHLITOMA ZEBRA IN CONFINEMENT. 385 



varying from 7 mm. to 3-75 mm. in length, and from 5*5 mm. 

 to 2*75 mm. in width. 



Growth. 



The young molluscs of the different broods varied in size and 

 rate of growth ; specimens of each of the earlier broods have 

 been figured at intervals to show the latter (Pis. I. & II.). As far 

 as possible the same individual was represented, but when one 

 died another of the same brood was substituted. The rate of 

 growth was not always uniform, and sometimes a smaller specimen 

 surpassed a larger companion. The difference in size was shown 

 in a remarkable manner in the case of the latest brood of v&r.ful- 

 gurata (September 1919), which consists of the grandchildren of 

 the specimen originally brought home. Three clays after discovery 

 the largest measured 20 mm. in length and 15*5 mm. in width, 

 while a week later the smallest, which was probably hatched from 

 an egg, had a length of 10 mm. and width of 9 mm. On May 4th, 

 1920, about six weeks after they ceased hibernating the smallest 

 was the same size as before, while the largest had a length of 

 22 mm. and width of 16*5 mm. There was also another remark- 

 ably small one. These two small examples were not long-lived, 

 for the first-mentioned died on May 27th, when it measured 

 10 mm. in length and 9-5 mm. in width. The second died in 

 October, when it was 13 mm. in length by 10-5 mm. in width. 

 A living companion of average size at this time measured 42 mm. 

 in length and 29 mm. in width. This last, and the rest of the 

 brood, were then commencing to hibernate, so I did not wish to 

 disturb them to make further measurements. 



The drawings represent the first broods up to the age of three 

 years and four months, when (September 1917) only one specimen 

 of each form was living. Neither of these had been figured 

 before, and they were then figured with the animals (PI. III. 

 fio-s. 1 & 2). At that date this specimen of var. fulgurata 

 measured 71 mm. in length and 41 mm. in width; var. obesa 

 57 mm. in length and 39 mm. in width. 



In September 1918 var '. fulgurata measured 81 mm. in length 

 and 46 mm. in width; var. obesa 77 mm. in length aud 49 mm. 

 in width. 



In September 1919 var. fulgurata measured 88 mm. in length 

 and 49 mm. in width ; var. obesa 80 mm. in length and 52 mm. 

 in width. At death var. fulgurata had attained a length of 

 89 mm. and width of 50 mm. ; var. obesa a length of 80 mm. and 

 width of 52 mm. It must be noted that both grew most between 

 September 1917 and September 1918, and least during the last 

 year of their lives. The increase in all cases was actually made 

 after hibernation, between the months of January and September 

 of each year. Var. fulgurata did not attain the length of its 

 parent, which was 107 mm. ; but var, obesa exceeded the size of 

 its parent (smaller specimen), which only measured 68 mm. in 

 length and 47 mm. in width. 



