330 Toyama, Mendel's laws of heredity a.s applied to the silk-worm crosses. 



B. Mixed offspring of " striped whites" (155 =73,81 °/ ), -'Japanese 

 normals" (40 = 19,04 °/ ) and no-marking whites (15 = 6,14°/ ). 



C. A mixture of "striped whites" (283 = 62,74 °/ ), "Japanese 

 normals" (86 =19,07%) and no-marking whites (82 = 18,1 8 °/ ). 



D. A mixture of "striped whites" (103 = 76,86 °/ ) and no- 

 marking whites (31 = 23,13 °/ ). 



The fourth generation. 



We have reared striped worins and Japanese normal marking 

 ones from B and C in the last generation. 



Some of the "striped whites" came true to parents, some pro- 

 duced a mixture of striped (73,43 °/ ) and „Japanese normals" 

 (26,56°/ ), while the rest a mixture of striped (78,23 °/ ) and no- 

 marking white worms (21,76 °/ ). 



Similarly, some of the "Japanese normals" produced simply 

 the offspring similar to parents, while the rest produced mixed broods 

 of "normals" and no-marking worms in the proportion of 76,54% 

 and 23,45 °/ . 



It is of some interest to note here that as the result of this 

 cross, we have procured in the subsequent generations a con- 

 stant striped breed characterized by possessing those semilunar 

 markings on the dorsal part of the eighth segment, which are en- 

 tirely wanting in the original striped breed, while in the Japanese 

 normal breed they exist as constant and distinct markings. 



Thus we may say that we have succeeded in combining two 

 parent-characters into one form. 



It must not also be omitted to mention that in the crosses 

 between Japanese "normals" and European striped breeds we have 

 obtained worms in which the left and right half of the body 

 exhibited the maternal and paternal characters respectively. 



Now we will examine whether these complicated phenomena 

 of segregation accord with the Mendelian principle or not. 



Since both breeds 1 ) used for experiments are not pure, the 

 dominant forms selected at random may be either pure dominant 

 (S in the striped breed, C in the Japanese "normals") or hybrid 

 dominant (SN in the striped breed, CN in the Japanese "normals"). 



Hence in the first crosses between striped and Japanese "nor- 

 mals" we may have the following combinations: 



1. (G-j-N)S = a mixture of two seemingly striped forms in 

 equal proportion. - 



2. (S -j- N) C = a mixture of 50°/ °f tne seemingly striped forms 

 and 50°/ of seemingly normal forms. 



1 ) S — pure striped; C = Japanese pure normal ones; N = pure no-marking 

 form; CN or SN = hybrid form of these two characters. 



