1912.) R. B. SEYMOUR-SEWELL : Surjace-Living Copepoda. 319 
Observed size. Calculated size. | Growth-factor. 
mim. mm, 
Stage 5 er $e | 0°844 0°844 I°5 
» 4 a are 1°295 1266 HOLY (036 a7) 
Ap as) Be + | 1°O11 1608 | rcs 
2 of Af | 1°880 1°399 
ig! a Sid 2'429 2°AI2 
At first sight the observed length measurements of the various 
stages did not appear to fit into ‘‘ Brooks’ Law,’’ but a further 
study revealed the fact that at stage 4 we have a division taking 
place and an individual may go through one of two processes, 
either he may at once proceed to stage 2 becoming sexually 
mature in a single moult or he may have an extra immature 
moult, reaching stage 3, and then by a final moult attain to stage Tr. 
The growth-factor between stages 5 and 4 is 1'5, and at the next 
moult some with the same growth-factor reach stage 2, others 
have an intermediate moult, the growth-factor of which is 1°27, 
(i.e. the same as that for the final two moults in the females) and 
then by a final moult having again a growth-factor of 1°5 he 
reaches stage 1. The number of examples of stage I was always 
considerably less than that of stage 2, and it is possible that these 
two forms may be seasonal dimorphic forms, the one a summer 
and the other a winter form. 
As regards the structural characters of these various stages 
I have given a detailed description below ; suffice it to say here that 
in both males and females, the last two stages only (stages I anid 2). 
as in the Halocypridae, are sexually mature and in both cases 
there are, as I have already indicated, considerable differences in 
structure between the invididuals of the two groups, so much so 
that if only a few specimens had been met with I should without 
any hesitation have described them as different species. This dif- 
ference was most marked in the case of the males, those of stage 
2, which become sexually mature direct from stage 4, being to- 
tally different as regards their grasping antennae and 5th pair of 
legs from the individuals of stage I, in which an intermediate 
moult is carried out. 
In order to check the results, I carried out a further series of 
measurements on specimens obtained in a tow-netting taken off 
Chittagong (approximately 620 miles away) in which the same 
forms were present. I obtained exactly similar results, and the 
measurements found are shown in text-figure IT. 
In the table below I have again given the average length- 
measurements of the various stages, as found, and the calculated 
size for reference. 
