196 JOURNAL OF CONCHOI.OGY, VOL. II, NO. 7, JULY, I905. 



the mother ; in experiment 53, the 5 (of experiment 49) was the 

 mother, and the records of these families shew, as far as they go, 

 that .the result of c^ o x $ 5 is not different from that of $ o x (J 5. 

 To the second class belong experiments 55-66, of which experi- 

 ment 55 may be taken as an example : of the fifty-nine young, thirty- 

 seven were unhanded, and twenty-two were banded. 



Lang's Interpretation of the Result of the Matings of 

 H. hortensis. 

 Lang maintains that the results of experiments 49-54 shew that 

 unbandedness is a dominant character in the Mendelian sense ; and 

 that five-bandedness is recessive. The results of experiments i to 38 

 are consistent with this, for, as we have seen, five-bandedness breeds 

 true, while 0x0 sometimes produces only o, and sometimes o and 5, 

 in experiment 42 in the proportion three to one. The appearance of 

 5's from o X 5 in experiments 55-66 is attributed by Ling to an 

 impurity in the strain of the o's ; the possibility that the unhanded 

 parents in these cases may have been heterozygotes, will be dis- 

 cussed later. 



Cross retween H. nemoralis and H. hortensis. 

 Ill only one instance has this cross been successful. The specimen 

 of ^ hortensis had tlie formula o'; the H. nemoralis was a 5 with fusion 

 of bands i and 2 together, and 4 and 5 together ; the lip of the shell 

 was, characteristically, black-brown. There are six offspring that have 

 attained an age at which they can be described." The following is a 

 summary of their characters : — 



a, In size they are intermediate between the two parents (only 



four of the six are full-grown). 



b, In three of them the altitude of the shell is much greater than 



that of either parent. 



c, All of them are unhanded, i.e., like the JI. hortensis parent. 



d, The lip in the four cases in which it is described, is dark, i.e., 



like the H. nemoralis parent. 



e, The shape and size of the lip is like that of H. hortensis. 

 Lang proceeds from this description of the hybrids, to a discussion 



of the specific distinctness of H. hortensis and H. nemoralis, and 

 deals with the evidence for the existence of natural hybrids between 

 them in the field. He cites the work of Coutagne,^ who sums up 

 his conclusions in five theses, three of which I quote here : — 



1 From the fact that no mention to the contrary is made, it may be concluded that the 

 H. hortensis hrid a white lip to its shell. 



2 p. 497. 



3 " Recherches sur le polymorphisme des Mollusqiies de France." Lyon, 1895. 



