Plates XXVI and XXVII. The First-Stage Lobster. 



The first-stage larva at the age of three days has a length of about 8 mm. The 

 accompanying figure shows the larva in the normal swimming position with the 

 abdomen bent at an angle of about forty-five degrees from the plane of the cep- 

 halo-thorax, which is in turn bent about forty-five degrees from the horizontal. 

 The eyes are large and prominent. The thoracic appendages bear the swimming 

 attachments, the exopodites, by whose rapid vibratory strokes the larva is kept 

 up in the water, and by whose m.otion, backward or forward, the movement of the 

 lobster is accomplished. The abdominal appendages have not yet appeared, 

 though they often may be seen as buds beneath the cuticle on the under side of 

 the abdomen. The tail or telson has the shape of a simple fan, whose posterior 

 margin is bordered by short spine-like setse. 



