THE YOUNCi OF THE CRAYFISHES ASTACUS AND CAMBARUS 43 



a wide augle with the main axis, toward the tip tliey become more nearly par- 

 allel with it and thus a fine terminal brush is formed by the main axis coming 

 gradually to an acute point in the midst of the surrounding side branches. 



The eggs are fastened to these plumose hairs by a secretion that probably 

 comes out of the glands of the pleopods (Andrews, :0()-). They then look as in 

 figure 45, which represents the anterior face of a pleopod cut off in the afternoon 

 of April 18, 1905, from a female that had laid the night before. Most of the 

 pleopod is concealed by the eggs which are opaque yellow balls and very elastic. 

 The plumose setae are all bound together by a common cement or mass of glaire 

 so that the individual setiB are not seen. From this mass a clear, flat, glassy 

 band of material goes out to each egg. Upon separating the eggs these bands 

 are seen as clear, flat stalks, continuous at one end with the mass that binds the 

 setae together and at the other end with the envelope about the egg. While the 

 shorter bands are flat and wide the longer bands are more string-like and some 

 few are twisted. Though these stalks may cross one another and be more or 

 less intertwined they are not fastened to one another. As the set:e spring 

 chiefly from the side of the pleopod and the eggs are tied to the setse, the eggs 

 may be combed out, as it were, into groups on each side of the endopodite 

 and of the exopodite. Where the stalk joins the egg it is enlarged as a bell, or 

 tent, full of liquid and its edges are continuous with the outer layer of the egg 



cai)sule. 



Each egg had then its own separate stalk, though a very few exceptions 

 sliowed tAvo stalks connected with an egg at different points and with a com- 

 mon extension running over the surface of the egg from one stalk to the other. 



Thus very firmly attached to the mother, the eggs are waved back and forth 

 by the mother who regulates the movements of the pleopods in accordance with 

 the oxygen supply in the water, and thus they slowly develop till they hatch. 

 The old egg cases and stalks still remain fast to the pleopods, and are of 

 use to the larva as a means of prolonging its life of dependence upon the 



mother. 



We will next describe' the way in which the first larva is connected with 



the mother. 



In hatching, the larva comes slowly out of the t'ii;^ capsule through a rent 

 along its back, in such a way as to draw out tiie legs and abdomen last of all as 

 represented in figure 8 in a previous paper (Andrews, :04). In fact the tip of 

 the abdomen remains inside the egg case long after the soft, helpless larva is 

 extruded and left dangling down into the water. And all these newly hatched 

 larvae would fall to the bottom were it not for a firm attachment of the tip of the 

 abdomen inside the egg case. As it is some time before the respiratory move- 

 ments become perfect, as the limbs only gradually acquire ability to move, and as 

 the body is globose and the creature cannot stand on its legs, the larva would 



