316 Records of the Indian Museum. [Vou. VIL 
I have embodied the results obtained in the following paper 
and for the sake of convenience I have divided it into two parts 
dealing respectively with the developmental changes in certain 
species and with a full description of the new forms obtained. 
I. DEVELOPMENT. 
From time to time results have been published showing that 
in certain members of the Crustacea the animal during the course 
of its development, as each succeeding growth-moult takes place, 
increases in size by a definite proportion. 
W. K. Brooks (1886, p. 105) was the first to show that such a 
mathematical relationship existed between the successive larval 
stages of the Stomatopoda. 
Hadley (1906) has shown that a similar condition of affairs 
is met with in the American lobster, Homarus americanus, Milne 
Edwards. Unfortunately I have not been able to see this paper, 
but Herrick (1411, p. 362), in his work on the natural history of 
this animal, has reprinted Hadley’s results. In the table given he 
shows that during the earlier moults the growth-factor is 1°18 
and that after the 17th moult this gradually diminishes. 
Fowler (1909) has also shown that in all probability the same 
condition of affairs exists in the case of Carcinus maenas, but 
his chief contribution deals with a group of the Ostracoda, the 
Halocypridae. He has shown that here also, at each successive 
moult, there appears to be a definite increase in the size of the 
animal and he has formulated the following law which he pro- 
poses to call ‘‘ Brooks’ Law,’’ that ‘‘ during early growth each 
stage increases at each moult by a fixed percentage of its length, 
which is approximately constant for the species and sex.”’ By 
applying this law, he has shown that as far as this group of the 
Ostracoda are concerned, it would appear highly probable that 
every species possesses two dimorphic forms corresponding to the 
two final sexually mature stages. 
With a view to testing whether the Copepoda followed the 
same law, I carried out a number of measurements of the various 
stages in the species Labidocera euchaeta, Giesbrecht, Acrocalanus 
ineymis, sp. nov., and Pontella andersom, sp. nov. The measure- © 
ment taken was the total length from the most anterior part of 
the head to the tip of the furcal rami, and the results were plotted 
out as shown in the following text-figures, the females being to 
the left and the males to the right of the middle line. 
(a) Labidocera euchaeta, Giesbrecht. 
In this species I have been able to obtain a fairly extensive 
series of measurements, covering six successive stages of growth 
in the female and four in the male. Of these stages, stage 2 and 
all below it undoubtedly were those of Labidocera euchaeta, but as 
regards stage 1, I was for some time of opinion that I was here deal- 
