THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBAEUS 41.' 



nuinl)er of niuults 80 that there were six in the second summer, if hot. Finally 

 Steffenberg ('72) gave the lengths of the Astaens larvae in Sweden as 8.5 mm. at 

 hatching; 11 nnn. in the second stage; 13 mm. in the third stage; 15 mm. in the 

 fourth stage. 



Asfacus leniusculus thus agrees closely with the Astacus of Sweden in the 

 length of the larva in the first, second, third, and fourth stages. As far 

 as the facts go it seems evident that Astacus leniusculus probably has mqre 

 larval stages than have been described for the first year young of the French 

 Astacus, but the differences are probalily due more to difference in food and 

 in temperature than to any innate differences in the species. 



With this close agreement in larval life between the American and Euro- 

 pean Astacus and the demonstrated success of rearing in the laboratory the 

 large young from the eggs brought overland, the culture of the American As- 

 tacus should be as siiccessful when landertaken as has been crayfish culture in 

 Europe. As elsewhere remarked (Andrews, :06"; :06^) the introduction of 

 the western Astacus leniusculus into Eastern waters might not only prove of 

 economic value but also help to throw light upon the interesting problem of the 

 nature of the causes that have brought about the |3i'esent remarkable geograph- 

 ical distribution of crayfish. And the geographical distribution of crayfish is 

 intimately connected with the origin of species in this group. 



Cambarus affinis. 



As elsewhere described (Andrews, :04) this connnon crayfish of Maryland 

 and adjacent States lays its eggs in the spring, and the development of the 

 young can l^e followed in the laboratory. Preparatory to laying, the females 

 carefully cleanse the parts of their bodies to which the eggs are to be attached 

 and the eggs flow out of the oviducts into a mucous mass which covers the ple- 

 opods upon which, after some special "turning" movements of the female, the 

 eggs are found attached each by its own stalk (Andrews, :06). 



The hatching young thus find themselves ui)on the abdomen of the parent 

 and here, as in Astacus, there are special contrivances which prolong the connec- 

 tion of parent and offspring for some time after hatching so that the attainment 

 of a free and independent existence is a slow and gradual process. 



The special arrangements used in the attachment of the egg and of the larvjB 

 in the first and second stages form a series of interesting adjustments between 

 the adult and the next generation. These successive means of association of 

 mother and oft'spring will be described in what follows. 



We will first consider the egg and the maternal appendages. 



The eggs, while numerous, three to six hundred according to the size of the 

 female, are small, scarcely 1.5 mm. as compared with 2.5 mm. in Astacus len- 

 iusculus. Some few become fastened to seta^ upon the abdominal sterna but 



4 



