256 



THE AMERICAN NATURALIST [Vol. XLI 



When fastened to tlie mother each egg was in a remarkably 

 elastic case wliich had a rongli, dirty outside layer and a clear 

 inner layer containing the same microscopic drof)lets seen in C. 

 affinis and similar to the droplets coming from the pleopod glands. 

 Each case was continued on one side as a long stalk that in turn 

 was continuous with the hardened secretion binding together the 

 plumose sette along the edges of the pleopods. The stalk was 

 hollow though flat and wide and was a continuation of the dirty 

 outer layer of the egg case, separating from the inner layer on one 

 side to form a large hollow^ bell or tent. 



Between the egg and the egg case was a variable amount of 

 coaguhnn showing fibrils in it. 



By April 17th some of the larvie had hatclied while otliers were 

 not yet out of the egg cases. The young, figure 1, had the usual 

 embryonic look of crayfish at hatching; a huge swelling of the 

 head region owning to the presence of nuicli yolk there; a weak 

 development of the locomotor part of the head-thorax so that the 

 five pairs of weak legs all arose posterior to the iriiddle of the head- 

 thorax; a weak, down-bent abdomen of little use in locomotion; 

 eyes almost sessile and of little size or perfection. These larva; 

 were transparent and showed the heart beating rapidly and the 

 scaphognathites rapidly baling the water out of the gill chaml)ers. 

 'Hie dark area in figure 7 represents the dark red yolk mass; 

 and the scattered dots, the aborescent pigment cells that w^ere 

 thickly scattered over the head-thorax and abdomen with but few 

 upon the third maxillij)ed, ba^e of antenna, three basal segments 

 of the antennule and some few segments of the periopods. 



Normally the larva- remained n])oii the mother and did not 

 move aboiU, and when jHiiled olV and put on the bottom of the 

 <nsh thev couhl iK.t Mand up but eonhl progress by lying upon 

 the side and llappino. the alnlonuM.. 



At halc.hin,-. figure 1, the young w.-re .o weak they would 

 have dropped to ilw bottom but for the " telsou-lhread " whicii 

 i. the cast otr ••uticle pulled ,Mit into a thread or band and fastened 

 at one end to the WUm of the larxa by the ^p.vial uU>u .pines 

 deMTibcd above and at the other end to the in^idr uf the rn.v. 

 A. th(- egg ease still tvinaiii> faM by it> >taik to the mother the 



