Development of Estheria Packardi. 



I. Larval stages. 



The larval development may conveniently be divided 

 into 6 successive stages, to be described below, each 

 of the stages being characterised by several well-marked 

 changes in the organisation of the larva. During this period, 

 which comprises about 4 days, the larva casts off its skin 

 several times, though the stages here described do not in 

 every case seem to be accompanied by a true exuviation. 



First larval stage. 



(PL I, figs. 1 & 2). 



The recently hatched larva is very small, scarcely ex- 

 ceeding in length 0,20 mm. It exhibits all the characters 

 of a true «Nauplius», being even somewhat simpler 

 than the well-known typical Copepod-Nauplius, in so far as 

 one of the 3 pairs of limbs characterising the Nauplius- 

 stage, viz , the antennulæ, are quite rudimentary. 



The body is divided by a median instriction into 2 

 divisions of nearly equal size, the anterior one representing 

 the cephalon, the posterior the still quite simple and unseg- 

 mented trunk. The anterior division is very convex above, 

 and, as it were, bulbously inflated, being obtusely rounded 

 in front; the posterior one exhibits a regular oval form and 

 has posteriorly a very slight notch. 



Quite anteriorly, just within the frontal part, a very 

 conspicuous, purplish red pigmentary patch, of a somewhat 

 irregular quadrangular form, is seen. This is the simple eye 

 or ocellus. Of the compound eye, on the other hand, not 

 the slightest trace is yet to be detected. 



