406 



EMEiUJENCt; Uf DUAiiONt'LV-LARV^, 



irt<(>iili(i(ii'(il ri'(jli>it iff strongly distended with blood, in which, hotc- 

 ever, no corpuscles are visible. A search througli the whole series 

 of sections hkewise fails to show the presence of any special organ 

 which might be interpreted as the collapsed cephalic heart. 

 There is nothing to be seen except the usual organs of the head 

 and thorax present in any insect-larva. If we combine these 

 two facts together, the conclusion is very strong that the cephalic 

 heart is really only (t special temjwrary developvient in the teso- 

 phmjns, and that, therefore, the pumping of the liquid blood must 

 take place through the month. 



cla ^^ cr c£v 



-Vll 



\(\^- 



fg... 



]r- 



Text -fig. 2. — Nearly median, sagittal section through pronymph of Anax 

 jinpHnnsis Biirni.. with the pronyniphal sheath removed. To show 

 mass of blood-coaguhim, without corpuscles, distending the reso- 

 phagus and crop. ( x l(Ml) : l>r, brain; cr. crop; da, dorsal aijrla; 

 ffj, frontal ganglion; ,7, -.7,;, thoracic ganglia; ,'/z, gizzard; Im. labial 

 mask (cut off); Ir. labrum; m, mouth; ;»//, muscle; >rs, (esophagus; 

 » r, fvsophageal valve (junction of fore- and midgut); i^orf, subicso- 

 ])hageal ganglion; 'vV, vitellophags in ^\all nf midgut. 



Let us now see how this conclusion agrees with the observed 

 facts of the hatching of the egg. Before the pronymph emerges, 

 there is a large '' head vesicle" fitting closely under the pedicel of 

 the egg. When the cephalic heart comes into action, the liquid 

 in this vesicle (which must obviously be a space between the 



