512 Miscellaneous. 



wood. The byssiis consisted of not more than half-a-dozen threads, 

 but bore a tolerable strain without breaking. I have not broken the 

 byssus ; the threads are pretty close together at the point of attach- 

 ment, which is perhaps two lines in width, and not spread over a 

 wide base, as is often the case with the Mussel. I have returned the 

 animal to the tank, in the hope that it may either shorten its hold, 

 or adapt its position to its altered circumstances. 



Leeds, May 18th, 1859. 



Fertile Hybrids of two species of Insects. 

 By M. Guerin-Menevtlle. 



Last year I succeeded in getting some females of Bombyx Cynthia 

 fecundated by males of Bombyx Arrindia, and vice versa ; and the 

 eggs laid by them produced caterpillars. These caterpillars, reared 

 last autumn, have shown nearly all the characters of Bombyx 

 Cynthia, which is the wilder and more vigorous of the two species. 

 Their cocoons, although resembling a little those of Bombyx Arrindia -> 

 by their deeper colour, conducted themselves in the same manner as 

 those of Bombyx Cynthia ; that is to say, being kept in a similar tem- 

 perature, the moths did not come out in the winter, as those of Bombyx 

 Arrindia constantly do. However, the influence of this latter species 

 has been felt from this first generation ; for, having placed some 

 hybrid cocoons in the reptile- room of the Museum, where the tem- 

 perature is never below 13° Centigrade, the moths came out at the 

 end of March, whilst those of Bombyx Cynthia proper, which I had 

 placed by their side for comparison, have not stirred yet. The moths 

 produced by this hybridation show on the whole, as their caterpillars 

 have done, more of the character of B. Cynthia than of B. Arrindia. 

 They are larger ; their abdomen is brown, with white tufts, — not white, 

 as in B. Arrindia ; the band across their wings is edged with rosy 

 atoms instead of whitish-grey, as in B. Arrindia : however, they re- 

 semble this species inasmuch as their wings are of a browner and 

 deeper colour than those of B. Cynthia. The species which pre- 

 dominates physically is B. Cynthia : but morally, so to speak, the 

 influence of the other species has been more strongly felt ; for the 

 hybrids of the two categories give caterpillars which, although re- 

 sembling those of B. Cynthia, are less wild or more domestic, which 

 assimilates them to the caterpillars of B. Arrindia. These hybrids 

 take from B. Arrindia the faculty of leaving their cocoons earlier, 

 without, however, continually coming out during winter; and it 

 is worthy of note that the hybrids obtained from the female B, 

 Cynthia and male B. Arrindia have come out a few days earlier 

 than the opposite hybrids. 



I may add that these hybrids are polyphagous, as nearly all the 

 Bombyces are ; for they may be fed with teazel-leaves, as well as the 

 ordinary silk-worms, which have been fed at all times with lettuce, 

 Scorzonera, goat's-beard, bind- weed, elm, rose-tree, and privet-leaves, 

 &c. — Comptes Rendus, April li, 1859. 



