NATURAL HISTORY OF AMERICAN LOBSTER. 305 



EGG LAYING. 



On two different occasions, as already related, lobsters which I had under observa- 

 tion laid eggs in aquaria, in the night or early morning. These eggs were fertile and 

 normally fixed in each case, but the extrusion was not complete, and the instincts of 

 the female did not run their normal course. In the absence of any direct observations 

 on the laying of eggs in the American species, the following account of the spawning of 

 the European lobster, given by Scott (248), has a special interest: 



The lobster turns onto its back and by the aid of the two large claws and ridge of the abdomen 

 makes a tripod of itself, the head being considerably higher than the posterior portion. The abdomen 

 is then strongly flexed, forming a pocket, and the setae on the edge of the abdominal segments make the 

 space along the sides perfectly tight. A A-shaped opening into the pocket is formed by the telson and 

 the sixth abdominal segment. This opening, when the abdomen is flexed, is slightly posterior to the 

 first pair of swimmerets. The eggs then flow from the two genital openings in a continuous stream, one 

 at a time, and pass along at the bases of the last walking legs and into the opening of the "pocket. " 

 The course of the eggs into the "pocket" is fiurther assisted by a constant pulsation of the first pair of 

 swimmerets, causing an indraft, which carries them rapidly inside. None of the eggs are lost on the 

 passage from the genital openings to the "pocket" unless the lobster is disturbed. As the eggs leave 

 the oviducts they become covered with an adhesive substance which causes them to stick together 

 and to the swimmerets. The period of oviposition in the lobster under observation was just over four 

 hours. Half an hour after the eggs had ceased to flow the lobster righted itself and walked into a comer 

 of the tank, eventually getting into a nearly perpendicular position, with the head downward. It 

 remained in this position for the rest of the day. Next day it was walking about the bottom of the tank 

 in the usual way of a berried lobster. That the adhesive power of the eggs was imparted to them before 

 leaving the oviducts was proved by collecting some just as they emerged from the genital openings. 

 When these samples were placed in a glass of sea water and collected into a heap , they all became attached 

 to one another and also to the glass. Moreover, the adhesive material only remains soft for a short time, 

 as when the individual eggs were isolated and prevented from adhering upon the glass it was found 

 that at the end of half an hour the adhesive property had entirely disappeared. 



ARRANGEMENT AND DISTRIBUTION OF EGGS AND THEIR ATTACHMENT TO THE BODY. 



Ishikawa, who watched the prawn Atyephyra lay her eggs in an aquarium, says that 

 the act is performed in the early morning, and that it is preceded by a molt the night 

 before, an order of events which has been often noticed in the higher Crustacea. The 

 eggs were "almost rod-like" when they came from the ducts, and were laid down in an 

 orderly manner, the anterior swimmerets receiving the first, while those deposited later 

 were driven backward by the last pair of thoracic legs. The abdomen was incurved 

 to form a pouch during the process, and the thoracic legs as well as the swimmerets 

 and their corresponding segments were in constant movement. 



In the lobster the ova adhere principally to certain setae of the appendages of the 

 five anterior segments of the abdomen (pi. xxxix), and since hairs are absent only 

 from the articular membranes of this region, they become bunched about the stalk of each 

 appendage, and extend over the sternal bar and inner (epimeral) wall of the correspond- 

 ing somites. In a full-berried female the swimmerets are embedded in a solid mass of 

 eggs up to their branches, comparatively few being fixed to the free blades, and these 



