No. 484] 



ATTACHED YOUNG OF CRAYFISH 



265 



As soon as out of the egg case tlic larvn lu'^aii to kick its legs 

 and in a few minutes the scaplioiiualliitc slowlv iiiovi'il, stopped 

 and began again, finally establishing a ra])i(l rliytlini. On adding 

 carmine, the currents made by the scaphognathite were visible 

 and its movement seemed comparable to a scooping motion of a 

 hollowed hand, the fingers downward, thus forcing the water 

 through the dorsal part of the respiratory passage as the fingers 

 closed the lower part and tlu-ii rising up to close the upper part 

 and prevent a back set of water into the passage way. 



Once out of the ego- cax- \hv hirva was still fastened to it by a 

 telson thread coii-^i-tiiiL;- of a -hovt ^wId'j: from tlie tel^oii spines to a 

 large cruniplc<l ma- that MTincd a cast otV cntich' and lay just 

 within the gaping egg case an<l \va> fasrcnc.l to it. in^'.h'. hy the 

 intervention of an expanded membrane which may possibly have 

 been the old vitelline membrane. This mend)rane wa^ t)omid to 

 the inside of the egg case by a few short fit)rils over a round area 

 smaller than the base of the egg stalk and often near it. Thus 

 suspended the larva moved its legs weakly and now and then shut 

 its claws and violendy flapped its abdomen without breaking 

 loose from the telson thread. Soon the larvje became fast by their 

 claws to the egg stalks or to the material on the plumose seta? of 

 the mother's pleopods. 



In this first stage the larva' remained cowered down close to the 

 pleopods and were so firmly fastened to the mother In' their claws 

 that they did not break loose when the pleopod was thrown into 

 Worcester's li(jtiid, though they jerked their legs and ])owerfnlly 

 and violently Happed their abdomens. Those left locked to the 

 pleopods of the mother lived three to four days and then molted 

 into a secon.l stage, May 2f>. 



They were very large. :, to (i mm. long when strct.'he.l ont and 

 4i mm. as they lay with the weak ahdomen carrie.l forward imder 

 the thorax an<l w<M-e very attractive ol)ject- hecan-e of the swaying 

 of the dark red and gol.len yolk nia>s, the contraction^ and change 

 in color of the lohes of the liver N|>read like the (iiiM-ei'- of a hand 

 deep in over the back, and of the liery. ruby-red. neuroiidike. 

 branching pigment cells >pangled over a hody so translucent as to 

 show the white blood corpuscles hurried along the vessels over the 

 red yolk, along the sinus at the edge of the (•ara})aee and out and 

 in through the legs an<l antemia> like shtitdes. 



