of the Fishery Board for Scotland. 



69 



makes the period one of three zoea stages, and between hatching and the 

 arrival of the young at the megalops condition there elapses from eight 

 to eighteen days. Saville Kent said that the European lobster reached 

 the megalops stage at about the sixth cast, i.e. five stages precede it, viz. 

 the protozoea and four zoea stages. A month or six weeks are occupied 

 in arriving at the stage beyond the megalops, which I have denominated 

 the first young stage. My own observations lead to the conclusion that 

 the period just mentioned will very rarely be exceeded ; it is probably often 

 as short as one month. Certain larvae which were in the zoea condition 

 in October and November remained for five weeks in one stage, however. 



Sars illustrates three zoea stages. Chadwick has published a descrip- 

 tion of the protozoea, three zoea stages, megalops, and first young stages. 

 The time occupied by each stage, with the exception of the protozoea, is 

 given as a week. 



Rathke says the maxillipedes and pereiopods have a general resem- 

 blance to the legs of schizopods, viz., Mysis, but the resemblance is 

 lost in the fifth pereiopod. In the denomination of the larval lobsters 

 it has been customary, therefore, to refer to the early pelagic stage as 

 the " mysis " stage. This is due to the fact that its pereiopods resemble 

 those of Mysis, in having setae-bearing exopodites. But this is an onto- 

 genetic, not a phylogenetic, character, as the name is apt to imply. The 

 main swimming organ of a zoea is the exopodite, and the number of 

 setose exopodites is directly proportional to the size of the larva. The 

 little elongated zoea of the shrimp (Crangon vulgaris) has three pairs of 

 exopodites in its first stage, but its increase in bulk in the third zoea 

 stage demands additional swimming power, and a fourth pair of exopodites 

 appear, viz. attached to the rudimentary first pereiopod.* In this case 

 the exopodite is developed, and becomes functional in the third zoea stage, 

 whereas the chela becomes functional for the first time on the megalops 

 stage, i.e. the sixth larval stage. The exopodite of the chela at the same 

 time vanishes, while the other exopodites, those of the maxillipedes, are 

 reduced and function no longer for swimming. In the case of the 

 lobster larva we have to deal with a large form, which requires a 

 powerful swimming organ. That is secured by the development of 

 the exopodites on the pereiopods, but with this difference from the 

 shrimp, that the pereiopods themselves are also functionally developed 

 — in the form of maxillipedes. The zoea of the lobster is provided, 

 then, with eight maxillipedes, each of which has a setose exopodite. 

 On the arrival of this form at the megalops stage the latter disappear or 

 are so reduced that they are no longer swimming organs. The quadrant 

 shape in which the body of the zoea is bent, by concentrating the 

 weight of the animal, has a direct relation to its propelling organs. The 

 tiny zoea of Carcinus mcenas has only two pairs of exopodites. It is bent 

 in an arc ; thereby the weight is concentrated. 



There, appears, then to be no valid reason for departing from the term 

 " zoea" for this period of the life of the lobster. And the term "mega- 

 lops " is an appropriate name for the stage which is analogous as well as 

 homologous to the megalops of the Brachyura. It is a transition stage 

 between the zoea and the adult. 



In this country the rearing of lobsters has been carried out by Saville 

 Kent, Cunningham, Weldon, Fowler, and Chadwick. On the Continent 

 Captain Dannevig has done the most extensive work in this subject ; 

 lately Appellof has carried on rearing experiments. 



Many difficulties meet the experimenter in lobster-culture. Questions 

 of the food, of the cannibalism of the larvae, and of the mortality which 



* Vide Williamson. 



