346 BULLETIN OF THE BUREAU OF FISHERIES. 



Hadley remarks that the adult structural type is possibly reached in the ninth 

 stage, and the adult color pattern in the eleventh. Inasmuch as single structural 

 characters, such as the differentiation of the big claws, are by no means regular or 

 invariable in their appearance, we should hardly expect to find the sum of such char- 

 acters expressed at a definite molt, which after all is but an incident of growth. Even 

 at the fourth stage, as Williamson {282) has shown in the European lobster, the swim- 

 ming organs are not shed in the same degree of completeness in all cases. Far less is 

 it possible to fix upon any definite stage when the sexual characters and sexual maturity 

 are reached. The data do not seem to be sufiicient to make the determination of aver- 

 ages very precise. Average length at seventh stage, Woods Hole, Mass., 18.6 mm.; 

 extremes, 18-19. 5 ™ni- (4 measurements); stage period, 14-21 daj's; Wickford, R. I. 

 (Hadley for 1904), average length 22.5 days; stage period, 14.3 days. 



THE EIGHTH AND LATER STAGES. 



The external structural changes which immediately follow the seventh stage are 

 very slight and concern chiefly the accessory reproductive organs, such as the differen- 

 tiation of the seminal receptacle of the female and the first pair of pleopods in both 

 sexes. 



The eighth stage is similar in color to the seventh, but according to Hadley there 

 is a greater modification of the slate color, with a tendency to develop the blue slate 

 and cream slate, or, in a less marked degree, the green slate and brown slate. According to 

 the same observer, the blue color is more pronounced in the ninth stage, when the 

 prominence of the white or cream colored spots is beginning to wane. It has been 

 further noticed that in the tenth stage the oUve green and olive brown combinations 

 become more prominent; the spottings are seldom seen, and the dark mottled charac- 

 ter of the coloring of the adult begins to assert itself. This characteristic mottled 

 color pattern was still more pronounced in the eleventh stage, when it was apparently 

 established. 



HABITS OF ADOLESCENT LOBSTERS. 



From the close of its free-swimming life until the later adolescent period the young 

 lobster drops out of sight so completely that for a long time its habits during this inter- 

 val were quite unknown (see i4g, ch. xi). After reaching the bottom we know that 

 many of the httle lobsters begin to travel toward the shore, in all probability slowly at 

 first, but more rapidly when at the age of about 3 months they have a length of i^ inches, 

 more or less. 



The instinct of fear, suddenly developed in the fourth stage and present at all later 

 periods, prompts the little animal to display great caution in all its movements, and to 

 hide under stones or in the crevices of any protecting object whenever danger assails it. 



Whenever the lobster sinks in very deep water, as must often be the case, it possibly 

 gradually moves shoreward. At all events many adolescent and small lobsters are 

 found along the rocky shores of bays and small inlets, where they apparently remain 

 until driven out by ice. These small lobsters live under stones and submerged rock 



