Tl IK AMERICAN LOBSTER. 



173 



topbores, great variety may be produced by tbe color of the gastric gland, which is 

 often orange or some cast of yellow, and by the contents of the alimentary tract, which 

 shows plainly through the body walls. Bright green pigment now appears for the first 

 time upon the dorsal surface of the carapace and upon the tergal surfaces of the hist 

 five abdominal somites. 



As in the first stage, the larvae thrive only on one another when kept in close quar. 

 ters. I have often watched one of these larvae as it attacked another which appeared 

 to be its equal in size and strength. The aggressive lobster usually tried to seize 

 his fellow by the small of the back or between the carapace and abdomen, using for 

 weapons the walking appendages, chiefly the first three pairs. He was soon astride 

 the back of his victim, and dragged him to the bottom of the jar, where he began to 

 devour him. 



The second larval stage lasts from two to five days. 



THE THIRD STAGE. 



The average length of the third larva in seventy-nine individuals examined was 

 11.1 mm., the extremes being 10 to 12 mm. 



The third larva resembles the preceding stages very closely in habits. Struc- 

 turally, it differs but little from the second larva. (Compare plates 21 and 22.) The 

 outer branches of the thoracic legs are still the principal swimming organs. However, 

 the last pair of abdominal appendages, which form the outer blades of the tail-fan, 

 are ready for service, and the swimmerets are fringed with short seta?. The large 

 claws, which were already conspicuous, are relatively much larger. 



COLOR. 



The third larva resembles the preceding stages closely in color. When the chro- 

 matophores close the animal is quite pale, as was the case with one which 1 examined 

 in the act of molting. As a rule, the color is enhanced by this stimulus. When this 

 specimen was examined with the microscope it was seen that the red chromatophores 

 were contracted so as to resemble small dots or stipple marks. The yellow pigment 

 cells were more irregular. 



When this transparent, almost colorless, larva is placed in a dish with others the 

 contrast is very striking. The colored form, in which the pigment cells are expanded, 

 is a rich, deep brown, varied with a vivid yellowish-green. The appendages are for 

 the most part reddish-brown, excepting the terminal parts of the smaller ones, such 

 as the exopodites and endopodites of the pleopods and the tiagella of the antennae, 

 which are bluish. The large chelae are a deep reddish-brown. The same color occurs 

 sparingly on the sides of the carapace and on the lateral and ventral surfaces of the 

 abdomen. The hinder parts of the carapace are touched with bright yellowish-green, 

 as are the third, fourth, and fifth terga of the abdomen. These intense metallic 

 colors greatly resemble those of the fourth larva. In reflected light a whitish pigment 

 is seen in the lateral eye, which is strongly iridescent, as in the earlier larva?. 



One larva (10.8 mm. long) has the thorax and upper half of the abdomen greenish- 

 blue; abdomen reddish below ; tail-fan reddish; red pigment cells occur on the append- 

 ages and on the sides of the branchiostegites, as in the earlier stages. 



In another, examined in the act of molting, on July 3, the colors were very bright. 

 Especially noticeable were the metallic green spots on the fourth and fifth abdominal 

 segments. 



