THE AMERICAN LOBSTER. 169 



usually singly, in a 4-gallou glass jar, which was covered with coarse linen scrim and 

 supplied with runuiug sea water. The mesh of the cloth soon became clogged, thus 

 fouling the water in the jar, which had to be cleansed daily. Under these conditions 

 young lobsters have been kept alive over 100 days and carried through ten molts. 

 The only food which they had beside that contained in the water was lobster eggs. 

 These were rarely touched by the very young larvae, unless they were lioated. Had 

 my stay at the seashore been prolonged some of the young could have been kept alive, 

 1 am sure, for an indefinite period, but other duties calling me away before the close 

 of summer, they usually died from lack of attention. 



There is now (August 1, 1804) alive in the hatchery of the Fish Commission sta- 

 tion a lobster which was hatched from the egg in June, 1893, and which is, therefore, 

 considerably over a year old. 1 The length of this lobster is only 36 mm., while three 

 lobsters which were hatched and kept alive until December 10, 1886, being then between 

 five and six months old, measured 35, 36.3, and 51.8 mm., respectively. 1 mention this 

 fact, now, to show how variable individuals are in their molting or, what amounts to 

 the same thing, in their rate of growth. It is improbable that such a marked variation 

 would occur in a state of nature, yet it is likely, as I shall later show, that even here 

 variation in individual growth is by no means slight. (See table 31 and p. 97.) 



Before describing the structure and habits of the larva we will glance at the 

 condition of the embryo at a late period in embryonic life. 



THE EMBRYO IN LATE STAGES OF DEVELOPMENT. 



A photograph of a living lobster with, external eggs taken in Cleveland, Ohio, 

 December 8, 1893, is reproduced in plate 7. A cluster of these eggs, showing how they 

 are attached to one another and to the set?e of the swiinmerets, is illustrated by fig. 25. 

 Drawings of the living egg and of the embryo teased from the egg capsule (figs. 

 26 to 28) give us some idea of the stage of development reached, in this instance, at 

 the very beginning of winter. Progressive stages of growth in the case of a lobster 

 whose eggs were laid July 1, 1890, and were beginning to hatch June 1, 1891, are illus- 

 trated by figures in the text. (Plates G to J.) 



At the stage shown in fig. 27 the bright green yolk occupies nearly one entire 

 hemisphere of the egg. This massive store of food, at the expense of which the organs 

 of the body are gradually developed, becomes reduced at the time of hatching (fig. 29, 

 plate 18) to a mere remnant within the stomach of the larva, and often undergoes 

 changes in color, at the last stage becoming a dull yellowish-brown. The paired com- 

 pound eyes have already become most conspicuous, both on account of their size and 

 color. The pigment area, which has a peculiar contour, is almost black when light is 

 transmitted or when reflected, except at a certain angle. It then glistens with great 

 brilliancy, owing probably to the interference of light in the thin peripheral pigment- 

 layer. Bright red chromatophores are distributed in a characteristic manner on the 

 appendages, particularly on their basal segments and along the sides of the carapace. 

 The yolk is divided by conspicuous dorsal and lateral indentations, corresponding to 

 the folds of the digestive tract and its diverticula, which gradually inclose it. 



During the course of development the ova increase considerably in size and, 

 losing their original globular form, become distinctly oval or oblong. 



See No. 1, table 33. 



