of the Fishery Board for Scotland. 



168 



In the first young stage (Figs. 164 and 169) the two tubercles are 

 present. The sternum is covered with the minute " needle-point " 

 cilia, except over the surfaces covered by the abdomen. 



Sexual characters are not seen. They were made out in crabs 

 measuring 5| and 5| mm. across. 



Sizes of the Different Stages. 



The drawings of all the stages are done on the same scale. 



Alongside the enlarged drawings of the I. -IV. Zoese and of the 

 Megalops, first and second young stages, outlines are placed representa- 

 tive of the natural size. 



In comparing the Zoea stages, the distance between the tips of the 

 rostral and dorsal spines was taken as the standard of measure- 

 ment. 



Stage. 



Number of 

 Specimens. 



Distance between 

 the Tips of Rostral 

 and Dorsal Spines, 



I. 





1-3:: 1-5. 



IT. 



1 



2. 



III. 



2 



2-3 : 2-4. 



IV. 



1 



3. 



Megalops and succeeding Stages. 



For the Megalops and succeeding stages two measurements were taken 

 of the carapace — (1) The greatest breadth. In all, except the Megalops, 

 this is at a fixed point, viz. behind the hindmost lateral teeth. (2) 

 Length of the carapace, i.e. the distance between the tip of the rostrum 

 and middle of the hind border of the carapace. 



1 



Stasre. 



Number of 

 Specimens. 



Greatest 

 Breadth. 



Mm. 



Greatest 

 Length. 



Mm. 



Megalops 



1 



M5 



1-5 



1 . 



2 



1-6 : 1-75 



1-7 : 1-7 



2 . 





2-4 



2-2 



3 . 





3-4 



3-1 



3a 





3-1 





4 . 





3-9 



3-3 



4a 





4-0 





