tgo1-1902.] The Entomostraca of Mid-Lothian. 309 
In all the copepods the egg-clusters are external: Diaptomus 
has only one, carried on the ventral surface of the abdomen ; 
while Cyclops has two attached laterally, one on each side. 
We have made several observations on the rate of reproduc- 
tion in Cyclops strenwus, by isolating two or three mature 
females and keeping them for some weeks. We found that 
about four days elapse between the formation of the egg- 
clusters and the hatching of the eggs. Two days after a 
brood is hatched, another pair of egg-clusters is formed, the 
whole process thus requiring only six days for its completion. 
About thirty young ones are hatched in each brood. We tried 
_ several times to rear the young ones, in order to observe the 
; moulting processes, but without much success. The longest 
time we succeeded in keeping a young one alive was twenty- 
nine days; in that length of time it had developed one fresh 
pair of limbs, and had, we think, moulted once. Our experi- 
ments were made in very cold weather, and we did not know 
what food to provide. At first we used to leave the mother 
Cyclops with the young ones after the latter were hatched; but 
it seemed to us that the young ones disappeared uncommonly 
_ quickly under these conditions, and we have a strong suspicion 
that the mother Cyclops fed on them in default of its proper 
food. 
The number of eggs in one brood varies greatly in the 
_ different species and genera of the copepods, but in all cases 
i the eggs seem to be produced and hatched in rapid succession. 
. Of reproduction in the ostracods we can say nothing ; ; com- 
_ paratively little is known of the subject as yet, and in many 
instances only the female of a species has been observed. 
When we come to the cladocerans we find two methods of 
reproduction. The summer eggs are carried about within the 
_ Shell of the parent until hatched. The number of eggs in one 
brood varies according to the species, such species as Chydorus 
_ spheericus or Bosmina longirostris having generally two to four, 
_ while certain Daphnias and Polyphemus pediculus may have as 
“many as twenty. The winter eggs are only one or two in 
_ number, and are contained in a case called the ephippium, 
- which forms at the back of the shell. In the autumn the 
_ ephippial females appear in large numbers; after a while the 
ephippium falls off without injuring the creature, and floats on 
Lain, 
Sate Orage. eee eprenee= ey 
