184
THE _BIOLOGY OF FISI-IES
£Ï':
…
As
by Iohs. Schmidt; these results are ,
strongly
variance with Mendelian expectations. We can
imagine, of course, that a special sex chromosome is present j
in the male and is a dominant, no matter what the—female
g
may be ; but one may reasonably hesitate to be led—intothe"
labyrinth of abstract possibilities when a simpler explanation
,
may be available.
{
It is a question of the origin of the pigment. There
.
maybe adeterminant or id in the germ which goes to form
pigment," but it is a general rule that pigment does not
the body of the embryo or larva until the red
,
blood-corpuscles are formed. It is thus apparently an
oxidation product depending on the metabolism of the
organism and on its movements.
On comparing now the .
-
maleforms A and Bof Lebistes, we nd that the B form has
'
'
plain :hÏomocercal tail along with the black spot on the
Ï
_
dorsal n.__ The form A has no black spot, but it has a "
peculiar tail. This is not quite symmetrical ; the terminal
portion of the hot0chord (urostyle). persists and a great
'
deal of variegated pigment, mostly red, is collected round
-
it and ”over the root of the tail (Plate V).
'.
'
._
From What has been said previously in Chapters IV and
V,- it seems probable that the form A represents “a younger -
stage of development than” form B, thus a slightly dierent
_
balance. _As this species develops at a phenomenâlly rapid
'
rate (the fully developed fry escape from_the mother-fish
_
in- about 3 weeks after fertilisation),- the difference between
__
the two
simply one of time and tempera—'
ture.
T he…_
advanced; and higher
.,
would probably in the course of a fewgçneratiens”: Changegitf‘i‘nto
pfeCocious ÎA form.
.
Ïi'jj
'
_
'
—
possibility Cannot
We can hardly
_
Say that the dilÏerençe between—A and B depends upon
the
'
'
inherited substance}; chromosomes or, the like.- _ If it does
.
1805 as ]OhS- Schmidthimsçlf points Out;we shouldhave the. .
.
.remarkable phenom€n0nof two
or. forms .,
,
..
depending upon a_.characœr'inhèœd
_
_
'
.
:
The most
'
suggeStive of Jobs… Schmidt’s_ experiments.