324 
Merism mid Sex in " Spinax Niger 
on the part of the for characters connected with the position of the pelvic fins. 
See Table 3, p. 32:3. 
(2) Comparison for emh-yos. It has been seen above that the average 
variability for the five characters taken is much greater for </ than for $ embryos 
(1174 to 1"057). The % embryos show a greater variability for the anterior spine 
but for all the four remaining characters the cfs are more variable, and in the 
cases of whole and half vertebrae (and possibly total segments) the differences are 
so great in comparison with the probable errors of the differences as to leave little 
doubt but that they are significant. Sec Tables 3 and 3 a. 
(3) Comparison of embryos with adults. It has been seen that the average 
variability is greater for the embryos than for the adults in the case of the (/"s 
(1-174 to 1-131) and less in the case of the ?s (1-057 to 1-132). The variability 
for the different characters is somewhat irregular, but there is a striking agreement 
between the way in which on the one hand the J" embryos differ from the J" adults, 
and the way in which on the other hand the $ embryos differ fi-om the $ adults. 
This may be expressed by saying that (a) where the (/ embryos are less variable 
than the adults, the $ embryos will be less variable than the $ adults and to 
a greater degree ; (/3) where the </ embryos and adults are equally variable the 
$ embryos will be less variable than the $ adults ; and (7) where the embryos 
are more variable than the cT adults, the $ embryos and adults will be equally 
variable. This point is exemplified in the subjoined table, which gives roughly the 
comparative variability of the embryos and adults in each sex. 
TABLE 3 a. 
+ signifies that the embryos are more variable than the adults. 
- ,) )) less „ „ 
[ ] signifies that the difference in variability is small and lies within the mean of the 
probable errors for embryos and adults, i.e. that there is in such cases practically equality 
of variability. 
Comparative 
variability of 
J embryo to i adult 
? embryo to ? adult 
Amount by which 
(J embryos are more 
variable than 
¥ embryos 
Anterior spine 
Posterior spine 
Whole vertebrae ... 
Half vertebrae 
Total segments 
- by 3 p. E.* 
[ + ] „ *i'-E. 
+ „ 3 p. E. 
[ + ] „ ^ r-E. 
+ „ 2 p. E. 
- by bh P. E. 
- „ lii'-E. 
[ + ]„ ^P.E. 
- „ 3 p. E. 
[ + ] „ JjjP. E. 
- 2i P. E. 
2" P. E. 
ih P. E. 
3' p. E. 
2 p. E. 
Hence the ^ embryos as compared with the (/■ adults show a relatively higher 
variability throughout (except for the anterior spine) than do the $ embryos as 
compared with the $ adults. Again, while the embryos are absolutely more 
variable than the ^ adults, the ? embryos are absolutely less variable than the 
* p. E. here signifies the mean of the two probable errors, i;e. that for embryos and that for adults. 
