OF COCHLITOMA ZEBEA IN CONFINEMENT. 383 



to the var. ftdgurata^ five or six weeks had elapsed since it had 

 the opportunity of copulation with its own kind, but there is the 

 possibility of its having been crossed with var. ohesa ; fertilization 

 in transit was unlikely as the specimens were tightly packed. 



The second brood (September 1915) of the larger specimen of 

 var. ohesa must have been produced either from the prolonged 

 eftect of the previous copulation, or else the mollusc must have 

 been fertilized afresh at least four months before, as that length 

 of time had elapsed since separation from its only fellow. As far 

 as can be judged from the appearance of the animals and shells, 

 cross-breeding does not seem to have taken place. It is, however, 

 a question whether the two broods of the progeny of the original 

 specimens may not be the result of cross- fertilization. The brood 

 of vn,r. fidgicraia (September 1919) was deposited about two years 

 and three months after the death of the last individual of its 

 own kind, aged three years, and after it had been living with 

 var. obesa about fifteen months. The actual parent of the young 

 ones deposited July 1920 is doubtful. If it was var. ohesa, and 

 fertilized by its own form, three years and four months had 

 elapsed since the death of its last companion, which was then 

 barely three years old. If fertilization was by A'ar. fulgurata it 

 may have taken place anytime after June 1918. If vsir.ftdgurata 

 was the parent, either the effect of the first copulation must have 

 continued or else there must have been crossing with var. ohesa. 

 The latter variety certainly laid some of the eggs, but it is not 

 evident whether any hatched. 



These last two broods are as yet too yo\mg to ascertain whether 

 there are signs of cross-breeding. The older one, however, bears 

 most resemblance externally to var. fulgurata. In connection 

 with this I would point out that Mr. Darbishire*, in an abstracit 

 of Prof. Lang's experiments with Helix hortensis and Helix 

 nemoralis, quotes an example of one of the snails being fertilized 

 in 1900, which, without further copulation, produced four families 

 in the years 1900, 1901, 1902, and 1903. Dr. Cooke t gives 

 instances of the prolonged effect of a single copidation in Helix 

 as2Mrsa and Avion ater. In the case of the former the first batch 

 of eggs was laid after the lapse of only four days, and the second 

 the following summer. In the latter a month elapsed, and then 

 this pair of Avion ater both laid batches of eggs at intervals 

 during a period of seven weeks. He also quotes from a paper 

 communicated by Mr. J. S. Gaskoin to the Zoological Society 

 in November 1850, to the effect that Helix lactea produced young 

 after being isolated four and a half years. 



Uggs and Young. 



It is of interest to note that these two varieties of Cochlitoma 

 have been observed to be at the same time both ovoviviparous 



* Jour. Coiicli. voL xi. no. 7, 1905, p. 194-. 



t " Molluscs/' Cambridge Nat. Hist. 1895, p. 42. 



