6 
the cuticle. Within a few days they cast their shell and 
assumed an appearance markedly different from the puerulus 
stage. The details of this transformation together with 
observations on the habits of the animal at this stage will 
be given elsewhere. This new stage may be called the post- 
puerulus stage as it is not yet quite like the adult. 
(3) Artificial Rearing of Cvrawfish—The hatching and 
rearing of crawfish has not hitherto been carried out with 
success in any country in which they are found. In Europe 
they do not occur in sufficient quantities to justify such 
experiments. They occur however in California and in Japan 
in large numbers where crawfish fisheries are of some con- 
siderable importance. Attempts to rear them have not 
hitherto been successful. The ordinary methods used for 
rearing lobster cannot quite be followed, as the various stages 
through which the crawfish passes before reaching the adult 
condition are very different from those of the lobster. In 
the case of the Cape crawfish our experiments have shown 
that there are two stages—the naupliosoma and the phyl- 
losoma—which are passed through before reaching the first 
stage of the young lobster. 
In the experiments which have been begun during this 
season our first endeavour has been to rear the young crawfish 
from the time of fertilisation of the egg up to the time of 
hatching. The crawfish carries its eggs externally for some 
months, and, during this time, they are hable to injury and 
attacks from other marine animals. It has been found that 
many fish devour the eggs in large numbers, especially about 
the time of spawning, and if the crawfish eggs can be reared 
under conditions which will keep them free from such enemies 
a great gain would be secured by such artificial rearing. 
Six female crawfish were selected with eggs believed to be 
at an early stage. They were placed in a well aerated tank 
and samples of eggs were taken from each crawfish twice a 
week up to the time of hatching. These were then examined 
microscopically by means of whole mounts and by sectioning 
so that the actual process of development could be carefully 
checked. It had however to be determined at what stage 
the youngest eggs were, and this was found by comparing 
them with eggs which had previously been seen escaping 
from the body of a female crawfish, the exact date of ex- 
trusion being therefore known. It was shown in this way 
that these youngest eggs were at a stage four or five days 
after fertilisation. This stage is characterised by the presence 
of about 20 nuclei at the periphery of the egg, each nucleus 
representing a blastomere or primitive segment of the egg. 
Seven days after, the nuclei had increased in numbers with 
a special thickening of the blastoderm at one spot. There- 
after development proceeded without interruption, through 
a nauplius stage, characterised by very long biramose antennae, 
