Development of Estheria Packardi. 9 



shape to that found in the 1st stage, and is now to a cer- 

 tain extent mobile, admitting of being somewhat raised and 

 again bent in against the body. Immediately inside its 

 terminal edge, several very large and distinctly nucleolar cells 

 are seen, apparently ot secretory nature. 



The alimentary tube appears now rather distinctly in 

 the axis of the body, being filled with yellowish contents, 

 which become dark brown in its posterior part. It is con- 

 siderably dilated in front, and exhibits here on each side a 

 short auricular expansion, the first intimation of the richly 

 ramified liver found in the adult animal. Posteriorly it 

 terminates with a very distinctly defined, and rather narrow 

 rectum, from which delicate muscular fibres radiate to the 

 walls of a surrounding cavity. 



The larva now moves rather quickly through the water 

 by rhythmical strokes of the powerful antennæ. By every 

 stroke the basal falciform process is seen to be thrown in 

 between the labrum and the body, towards the now formed 

 oral orifice, and it is therefore very probable that this 

 process is of essential service for bringing nourishing 

 matter to the mouth, for which reason it may properly be 

 termed the masticatory process of the antennæ. 



Third larval stage. 



(PL I, fig. 5). 



This stage immediately succeeds the preceding one, 

 being however rather sharply marked off from the same by 

 a previous complete exuviation of the larva, whereby some 

 very conspicuous changes have taken place. 



The form of the body appears still more elong- 



