204 'Journal of Comparative Neurology and Psychology. 



moulting, but never between moults. From the fourth stage on, 

 each successive stage-period is of longer duration and the changes 

 which the adolescent lobster thenceforth undergoes are corre- 

 spondingly less significant, being characterized chiefly by altera- 

 tions in internal morphology as the adult functional type is grad- 

 ually approximated. The first three stages of the lobster are 

 free-swimming stages, and the activities are without apparent 



Fig. 1. Showing a young first-stage lan-al lobster about two days old. The eyes are large and promi- 

 nent. The exopodites of the thoracic appendages are represented at the beginning of the downward 

 stroke. This figure shows the typical swimming position of larvae in the first three stages, the plane 

 of the cephalo-thorax bent down at an angle of about 30° from horizontal. 



coordination or aim. The larvae are swept here and there by 

 the tide and possess no power to evade the attacks of numerous 

 enemies. 



The swimming of the lobsters of the first three stages is accom- 

 plished by means of the feathered exopodites, or outer branches of 

 the thoracic appendages (Fig. i). These exopodites beat the water 

 with short vibratory strokes, which tend to carry the larva back- 



