Table 2.
| [A] This convenient form of zygotic formulæ, using a subscript 2 instead of doubling the letter, is proposed by Prof. W. E. Castle. | ||
| Type. | Zygotic constitution. | Soma. |
| a | M2L2[A] | Y |
| b | M2Ll | Y |
| b | M2Ll | Y |
| c | MmL2 | Y |
| d | MmLl | Y |
| e | M2Ll | Y |
| f | M2l2 | I |
| g | MmLl | Y |
| h | Mml2 | I |
| i | mLML | Y |
| k | mLMl | Y |
| l | m2L2 | oo |
| m | m2Ll | oo |
| n | mlML | Y |
| o | mlMl | I |
| p | m2Ll | oo |
| q | m2l2 | Absent |
It is a consequence of this second hypothesis that, in F2, of every 16 young 9 should have the Y comb; 3 the I comb; 3 the oo comb, and 1 no comb at all. It follows further that the progeny of two F2 parents will differ in different families. Thus if a Y-combed bird of type a be mated with a bird of any type, all of the progeny will have the Y comb.
From Y-combed parents of various types taken at random 4 kinds of families will arise having the following percentage distribution of the different types of comb:
- 1. Y comb, 100 per cent.
- 2. Y comb, 75 per cent; I comb, 25 per cent.
- 3. Y comb, 75 per cent; oo comb, 25 per cent.
- 4. Y comb, 56.25 per cent; I comb, 18.75 per cent; oo comb, 18.75 per cent; absent, 6.25 per cent.
Again, mating two extracted I combs of F2 should yield, in F3, two types of families in equal frequency as follows:
- 1. I comb, 100 per cent.
- 2. I comb, 75 per cent; no comb, 25 per cent.
Again, mating two extracted oo combs of F2 should yield, in F3, two types of families in equal frequency, as follows:
- 1. oo comb, 100 per cent.
- 2. oo comb, 75 per cent; no comb, 25 per cent.
Single comb × Y comb should give families of the types: