1881.] Fiddler Crab, and of Alpheus. 787 
Comparing our Gelasimus larva, artificially removed from the 
egg, with Faxon’s beautiful figures! (1, 2) of the embryonic zoéa 
of Carcinus shortly before hatching (his Fig. 9 representing the 
larva in the act of exuviating the larval skin);’ the first antenne 
are seen to be much shorter and proportionately stouter than in 
the remarkably developed antennz of Carcinus, being more as in 
the zoéa stage; the second antennz have nearly the same general 
form as in the zoéa after molting ; the spine (exopodite), squami- 
form appendage (endopodite), and rudimentary flagellum being 
indicated. The antennz of our embryo Gelasimus do not appear, 
then, to have the great development found by Faxon to exist in 
Carcinus of the same or nearly the same age. Faxon has not 
represented the first maxillz, but it is two-lobed, the lower larger 
lobe probably being later in life differentiated into two endopo- 
ites; the second maxille differ from Faxon’s figure of the em- 
bryonic zoéa of Panopzus in not being divided into four endopo- 
dites equal in size and form, but into three endopodites, the sec- 
ond (v en?) being deeply lobed, and the third (v en’) being two- 
jointed. They, however, are nearly identical in form with the 
second maxille of Cyclograpsus as figured by Miller.’ 
The endopodites of the first and second maxillipeds differ from 
those of Carcinus in having five joints, Carcinus having four 
joints to the endopodites of the first pair and only two in the 
second pair; in Cyclograpsus, however, Miiller figures three, and 
as Gelasimus stands higher in the series than Cyclograpsus, it is 
possible that Gelasimus is, in this respect, more differentiated. 
(All of my drawings were made with the camera, though it is 
possible I may have been in error in drawing too many joints.) 
he tail of our embryonic Gelasimus also shows no such 
extreme development as discovered in Carcinus by Faxon, and in 
this respect it is like Cyclograpsus (Miiller’s Fig. 18); and hence 
I am inclined to the supposition that Gelasimus before. the first 
*On some points in the structure of the embryonic zoéa. By Walter Faxon. 
sarong Mus. Comp. Zoology, v1, No. 10, Pl. 1, Fig. I. : 
We see no reason for not homologizing this membrane with the amnion of in- 
Sects and of Limulus and Apus. 
*See Facts for Darwin. English translation, p. 50, Fig. 18. Our Gelasimus zoéa 
‘ppears to agree much more closely with the zoéa of Miiller’s marsh crab (Cyclo- 
Stapsus) than with that of Carcinus or Panopzeus, but in Miiller’s figure the endopo- 
dites of the second pair of maxillipeds are drawn as three-jointed. His zoéa has a 
orate and frontal spine, and represents a more advanced stage than our Gelasimus 
em, ryo, 
