. Bulletin of the Essex Institute . i<iBe«ley. del. / V CRANGON VULGARIS. 147 parison of figs. 10 and 11 shows, as was mentioned above, aconsiderable difference in the size of tlie embryo, the olderbeing considerably the smaller of the two, the originaldimensions not being regained until the stage just (77), calls attention to a similar state of affairsin Eupagnrus, while Ishikawas figures show that thesame occurs in Atyephyra. In Astacus, according tomeasurements of Keichenbachs plates, there is a similarcontraction of the germinal area, though not to so great anextent as in the
. Bulletin of the Essex Institute . i<iBe«ley. del. / V CRANGON VULGARIS. 147 parison of figs. 10 and 11 shows, as was mentioned above, aconsiderable difference in the size of tlie embryo, the olderbeing considerably the smaller of the two, the originaldimensions not being regained until the stage just (77), calls attention to a similar state of affairsin Eupagnrus, while Ishikawas figures show that thesame occurs in Atyephyra. In Astacus, according tomeasurements of Keichenbachs plates, there is a similarcontraction of the germinal area, though not to so great anextent as in the other forms mentioned. So far as I nowrecall, this circumstance is not readily paralleled in theanimal kingdom, nor is it easy to explain. Indeed, I canthink of but one interpretation to be placed upon it andthat is not over satisfactory. It is as follows : almost alldecapods now leave the Qgg and begin a free life in a com-paratively advanced condition, but the evidence presentedby Lucifer, Pendens, etc., shows that their ancestors be-gan their fre
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