of the Fishery Board for Scotland. 139 
Tur LARVAL STAGES. 
The Larval stages of this form are divisible into three groups: (1) 
the Protozota stage: (2) the Zoéa stages, four in number: (3) the 
Megalops stage. 
Protozoéa (Fig. 160). 
The so-called Protozoéa stage was described by Du Cane, Spence 
Bate, and other authors. It is of very short duration. The larva 
leaves the egg capsule in the condition shown in the figure. It has 
neither the rostral nor dorsal spine. It immediately casts its delicate 
integument and appears as a Zoéa of the I. stage. 
I have not noticed the Protozoéa stage in cases where the larve 
have hatched out in a tank. It may however be got by washing the 
egg-mass of a female during the time the young are hatching. 
Faxon* gives a correct description of this stage, and it is not 
necessary here to recapitulate it. 
The Zoéa. 
The Zoéa is wholly pelagic. 
It is a feeding period during which the Pereiopods and Pleopods 
develop. 
FuncrionaL AppENDAGES. The Zoéa has a cephalothorax, and abdomen 
and telson. There is no sharper dividing line between the cephalon and 
the thorax than there is in the adult. The thorax is only partly 
developed, two thoracic appendages alone being functional, viz. the First 
and Second Maxillipedes. The hind part of the thorax, to which 
pertain the Third Maxillipede and the five Pereiopods, is rudimentary. 
The cephalic appendages are all present and functional: they are the 
Eye, Antennule, Antenna, Mandible, First Maxilla, Second Maxilla. 
The abdomen is 5-jointed ; the pleopods are rudimentary. 
All the functional appendages differ very much from their structure 
in the adult. 
With the exception of the telson they are feeding and sensory organs. 
The telson, as Du Cane pointed out, functions mainly in assisting the 
ecdysis of the integument of the appendages. (Cp. the telson in the 
Zoéa of Crangon vulgaris.) The abdomen and telson are also used for 
intermittent progression. The principal motor organs are the setose 
exopodites of the first and second maxillipedes. 
The Megalops, 
The Megalops is the connecting link between the pelagic Zoéa and 
the demersal young crab. It partakes of the characters of both. It 
swims by means of its five pairs of pleopods, after the manner of a 
Crangon, and also crawls about on the bottom by means of its 
pereiopods, 
In Crangon the Megalops stage persists with slight modifications to 
be the adult condition. The Brachyura pass through a Crangon stage in 
the Megalops, and then undergo further specialisation which affects the 
abdomen alone. The pleopods change in character, they lose the 
* “On some Points in the Structure of the Embryonic Zoéa [Carcinus menas and 
Panopeus Sayi),” Bull. Mus. Compar. Zoology, Harvard, vol. vi, No. 10, 2 pl., p. 159, 
Cambridge, Mass., U.S.A. ; 1880. 
