of the Fishery Board for Scotland. 137 
Thompson gave drawings of what he labelled the Megalops and first 
young form of Carcinus. He believed that they were derived from the 
Zoéa just mentioned. The Megalops and first young stage do belong to 
Carcinus menas, but they were not derived from the Zoéa in question, 
R. Q. Couch in 1843 described* the Zoéa of Carcinus, which he 
obtained by keeping the berried female in captivity until the eggs were 
hatched. He gave drawings of the Zoéa, Megalops, and first young 
stage of this form; the sketches of the two former are not diagnostic. 
Both Thompson and Couch regarded the Zoéa stages as one stage, and 
the Megalops as the second stage. While they recognised that the Zoéa 
grew larger, and that certain organs developed during the Zoéa period, 
they did not state distinctly that these changes in size, ete., are brought 
about by moults, not merely by gradual growth, Thompson also 
discriminated between young and full-grown Megalopa. 
Du Canet had in 1839 given a description with drawings of the 
Protozoéa and first Zoéa. 
The first exhaustive treatment of the Zoéa and Megalops stages was 
made by Spence Batet in 1859, In tracing the development of the 
Zoéa he drew attention to the fact that the changes from a Zoéa to the 
erab are gradual and not really of the nature of a metamorphosis. 
He said in this connection (p. 590)—“In the highest types of Crustacea, 
the immense variety of change from the Zoéa to the complete animal is 
but the result of swbordinate becoming more important parts, together with 
the development of others not yet present, and therefore hardly accept- 
able under the signification of metamorphosis.” ‘The author is 
perfectly aware that in Insecta the change of the animal within the 
chrysalis is gradual in development; but he wishes to show that there 
is no stage in Crustacea answering to the chrysalis; that the moults in 
process of development of the Crustacea are of the same kind as those 
which take place in the adult condition.” 
Spence Bate gave drawings of the appendages, and traces their 
development through a number of stages. They are, however, made on 
a small scale, and are to a considerable extent vitiated by the fact that 
stages belonging to species other than Carcinus have been introduced 
into the series. He depicted three Zoéa stages, of which the last does 
not belong to Carcinus. He did not satisfy himself as to the number of 
moults which take place in the Zoéa period, and he was of the opinion 
that the Megalops stage was a period of stages analogous to that of 
the Zoéa period. He had arranged two Megalopa and a young form 
into aseries. The first of these is nota Carcinus, the second and the third 
could not from the drawings be recognised as belonging to this species. 
There is only one Megalops stage. 
Brooke described the Megalops and six successive stages of Carcinus. 
He, following Spence Bate, regarded the Megalopa which he had collected 
as belonging to the last Megalops stage. His drawing of the Megalops 
does not show the characteristic long curved bristles which are present 
on the dactylopodite of the fifth pereiopod of this stage. 
Tue Hatcuinc PERIOD: THE OCCURRENCE OF THE Zota, 
No investigation was made with the view of finding out during how 
many months the Zoée of Curcinus were to be found in the sea, but 
* R. Q. Couch, ‘‘On the Metamorphosis of the Decapod Crustaceans,” Eleventh Annual 
Report of the Royal Cornwall Polytechnic Society, Falmouth, 1848 ; 1 pl. 
Du Cane, ‘On the Metamorphosis of the Crustacea,” Annals of Natural History, 
vol, iii., 1839 ; 1 pl. 
{ Spence Bate, ‘On the Development of Decapod Crustacea,” Phil, Trans. Roy. Soc., 
London, 1859, p. 589, pl. xl.-xlvi, 
