NATURAL HISTORY OF AMERICAN LOBSTER. 347 



piles, the tops or surfaces of which are sometimes laid bare at unusually low tides in 

 fall, when they may be found by digging and turning over the stones, at depths of but 

 a few inches at low water, but where at the flood the sea rises to a height of 5 feet or 

 more. The smallest, from about iX to 3 inches in length, go deep down among the 

 loose stones, where no enemy is likely to reach them. At a later period, when from 

 5)4 to 4% or 5 inches long, they issue from their retreats more freely and explore the 

 bottom with greater boldness. They also dig caves under stones, from which, as at an 

 earlier period, they stealthily crawl in search of prey, but quickly return when an enemy 

 appears. We have seen that this characteristic burrowing instinct develops as early 

 as the fourth stage. 



As the lobster increases in size it becomes bolder and retires farther from the 

 shore, but it never loses its instinct for digging nor abandons the common habit of 

 concealing itself when the necessity arises. 



A LOBSTER 413 DAYS OLD. 



As is well known, size, whether of lobsters or of mankind, is not a certain criterion 

 of age. In the crustacean it depends upon the number of molts successfully passed, 

 while unfavorable conditions tend to lengthen the molting periods. Some of these 

 conditions will be considered in a later section. This was well illustrated by the young 

 lobster whose history follows. This animal was reared in a small glass aquarium at 

 Woods Hole, Mass., and was fed with minced clams and the eggs of the lobster and cod. 

 It lived from June 20, 1893, until August 6, 1894, when it had attained the length of 

 36 millimeters (1.44 inches). 



In its final stage the colors of the animal had apparently reached the limit of their 

 brilliancy and the mottled color pattern was as complex as in an adult animal. The 

 body was of a light umber color freely speckled and mottled with darker tints. The 

 appendages were reddish brown and slightly translucent. Small light spots or suffus- 

 ions were found in certain parts of the body ; the tendon marks, corresponding to those 

 characteristic of the fifth and later stages, were prominent, the round spot just below 

 the cervical groove being over a millimeter in diameter; the pleura of the first abdominal 

 somite were snowy white, while the free edges of the segments of the body and of the 

 appendages were bright blue; the large chelae were white tipped. The openings of the 

 oviduct were plainly visible, while the lips of the copulatory pouch or seminal receptacle 

 were not yet closed. The color of the appendages on the under side was light reddish 

 brown, and the tail-fan was of the same hue, edged with deep red; the big claws, which 

 were tufted with setae at their tips, showed but little differentiation. The compound 

 eyes had acquired the large size and prominence of the later adolescent stages. 



WHEN DOES THE YOUNG LOBSTER GO TO THE BOTTOM TO STAY ? 



Over 15 years ago I raised the question which is now placed at the head of this 

 section, and answered it in a tentative way, but its importance seems to have been 

 underestimated, for it has received Uttle attention from other workers up to the present 

 time. 



