Habits and Early Dci'c!op>ncnt of Lincrgcs incrcurins. 157 



from tlie oral pole the successive axes of elongation (or flattening), in some 

 cases at least, pass slowly aronnd the hell in an anti-clockwise direction. 



In the normal forwartl movements the animal always rotates in an anti- 

 clockwise direction, when viewed from the oral pole. They may stand for 

 some time with the ahoral pole at the surface of the water and rotate rapidly in 

 the direction named, without much forward movement, but always with pulsa- 

 tions of the bell. The cause of this rotation lies in the lobes or lappets at the 

 margin of the bell, which is so arranged that the right side of each lappet 

 (when viewed from the center of the oral pole) lies nearer the oral surface 

 of the bell than the left side, and usually the right side overlaps the left side 

 of the next lappet to the right. Therefore, in pulsations of the bell, water is 

 directed out in a clockwise spiral, which causes the animal to rotate in an 

 anti-clockwise direction. If the lappets are cut off, the bell may continue to 

 pulsate, but the animal only moves forward slowly and does not rotate. If 

 a hole is cut in the aboral side of the bell and the stomach and manubrium 

 removed, the bell continues to pulsate and the animal moves forward nor- 

 mally and with anti-clockwise rotation, though these movements are slower 

 than normal. If the whole margin of the bell is cut off it continues to con- 

 tract for a long time, the movements being almost entirely such as flatten the 

 ring alternately in one direction ami then in another (second type of move- 

 ment described above). The remainder of the bell, after the margin has 

 been removed, is usually quiescent, but may sometimes contract slowly. If 

 the marginal ring is cut in two so as to form a long, narrow ribbon, it still 

 continues to contract rhythmically for several hours. 



Egg-laying. The males and females of this species may be distinguished 

 by the color of the ripe gonads ; the male gonads are brown, those of the 

 female slate or blue-gray. 



The eggs are laid and fertilized about 8 a. m., and at no other period of 

 the day. The egg-laying begins by the escape of a few isolated eggs from a 

 few individuals, but in a short time a perfect " epidemic " of egg-laying 

 takes place, after which no other eggs are laid until the following day. The 

 eggs escape in masses held together by a thin jelly. Occasionally small, 

 immature eggs are laid along with the mature ones, but this is rare; usually 

 all the eggs are mature when laid. Each egg is closely surrounded by a very 

 thin transparent membrane which persists until the gastrula stage. Out- 

 side this membrane are numerous small, brown bodies which are probably 

 follicle cells. 



The spermatozoa are shed at the same time that the eggs are laid, but I 

 was unable to determine whether one of these processes stands in a causal 

 relation to the other. 



The egg-laying usually takes place very close to the surface of the water, 

 after which the eggs gradually settle through the water to the bottom of the 

 aquarium. If the gonads have not been emptied on the first day the medusas 



