No. 484] 



ATTACHED YOUNG OF CRAYFISH 



255 



loosened cuticle and seemed fastened to it. On the ri^ht of the 

 specimen fine wavy lines sujrgested secreted films rather than fibrils. 



As will he seen later these specialized s})ines are ^^landular 

 stnictnrcs (hat make (he tcl.soii adhere firmlv (o the cast-off cuticle 

 and th.i.s make pn^iM,- di.' -U'lsun thr,'ad""cf the hatching hirva. 



The .mail uuml.er ..f .pine. -n.uped. touerher Nxilh the fact 

 thai the wUnu of eadier eml.rxonie .(a-e. i> in<-i.ed en the middh- 

 nf the posterior ed^e Mi^-ct. tliat the.e 7 or S .pine, max he 

 eomparal)le to the 7 nr S .pine, .ecu on ca-h .ide of the inei.ed 

 telson of the lobster cinl)r_vo (Fig. 72; Herrick; The American 

 Lobster) before it molts at the time of hatchini^ and is in a stage 

 which Herrick compared to a protozoea, or other early larva. 

 On this basis a very remote ancestral state has been retained to 

 the extent that its spines have been applied to the new use of 

 attaching the larva to its cast cuticle. 



Before speaking of the hatching larva' it must be recalled that 

 all crayfish eggs arc fastened to the ])leoj)ods of the mother by a 

 hardcnino- mas. whose oriuii. is somewhat in dispute. In' C. 

 clad-ii the pieopod. of the mother were so transhicent that the 

 transverse striation of the imiseh-s was seen through the exoskeleton 

 and with 2. 1). the gland cells that arc supj)osed to take part in 

 fixing the eggs to the pleopods were seen as polygonal areas of 

 secretion droplets separated by clear lines. 



All over the bases of the pleopods these areas were massed 

 together but the terminal part had them arranged in transverse 

 bands that crossed the anterior face and extended into the sides 

 but left the posterior face without glands. ( )n the bands anteriorly 



the glands to the surface and near these were .ome short, sharp 

 setie w^hich occurred a.uaiii at th(- tips of the ph-opods. 



While it is possibK- that thes(- .harp scta« aet in priekin- lUc 

 egg. and liberating an a Ihe.ixe material a. .'laimtvl in Wiiliam.on 

 for crab's egg., and that tlu^ u'lan.l. of the ph-opod. have nothinu" 

 1<) <lo uith fa.teidn- the e--.,\et tiii. .eem. ^rr^ improl,al>ie. a. 

 d.een-> are fa.tentMl to a lai-e'nia.. of material Minilar to the e-g 

 (•ii.e a-Kl .talk an<l uhieh bin. Is all the l.)!.- plumos<> .eia> together 



