56 INHERITANCE IN SILKWORMS, I 



of whether the double cocoon may not be the result of the labors of a 

 single one of the two larvae enclosed, the other being an individual 

 which for some reason is not able to spin a cocoon, and hence attempts 

 to become a room-mate with a normal spinning larva. She found in 

 a number of cases that by separating two larvae becoming enclosed in 

 a common cocoon only one of the pair made a cocoon, the other spin- 

 ning threads aimlessly or forming only a "carpet" and then pupating 

 unprotected by a cocoon. In one or more cases the two larvae be- 

 coming enclosed in a common cocoon showed by their attempts to 

 spin single cocoons after being separated (one always succeeding) 

 that they were spinners of differently colored silk. In no case how- 

 ever have we noted a double cocoon composed of two colors of threads. 

 Miss McCracken's observations and suggestions should be followed up. 

 A little attention has been paid to note whether, in association of 

 larvae in spinning of double cocoons, sex cuts any figure. Double 

 cocoons were often found to be produced by two females together or 

 by a male and a female working together, but we have no recorded 

 case of two males issuing from the same double cocoon. However, 

 our records touching this point cover too short a series to be at all 

 conclusive. 



APPEARANCE AND BEHAVIOR OF "SPORTS." 



In the seven years of our silkworm rearing there have appeared 

 in various lots individuals showing sport characters of several kinds. 



In 1903 various cocoonless pupae were noted, the larvae of these 

 having spun no silk at all, or only a random "carpet," or they outlined 

 cocoons only to neglect and leave them. Eight such cases were noted 

 in 1903. Other larvae spun only very thin, semi-transparent cocoons. 

 In 1904 and 1905 other thin or skeleton cocooners were noted. Also 

 larvae that spun up after the third moulting (instead of the fourth 

 as normally). Certain cocoons of extraordinary shape were also 

 noted. Certain larvae with caudal horn wholly wanting and others 

 with this horn very short and small were observed. (PI. I, fig. 12.) 

 A few larvae with curiously distorted body appeared (PI. I, fig. 8). 

 Also larvae showing sport characters of coloration and pattern (PI. I, 

 fig. 9). The moricaud or all-dark color-pattern of the larva was found 

 to be a frequent sport occurring in several races. (This has been the 

 subject of breeding and inheritance testing by Coutagne, Toyama, Miss 

 McCracken and myself and is referred to in the part of this paper 

 devoted to a consideration of the alternative or Mendelian character- 

 istics of the silkworm) . 



