1 62 Jo2irnal of Comparative Neurology and Psychology. 



havior, which during development give way to more complex 

 types leading up to the condition found in the adult. This 

 seems to be a matter of some importance, for the reason that 

 it indicates that it will be nearly or quite useless to look to lar- 

 val stages for help in analyzing the adult behavior in forms like 

 Limidus. It seems likely from what we know of the general 

 correlation between type of behavior and general type of body 

 form, that the same thing will be true in most cases where the 

 general form relations of the body are closely similar in larval 

 and adult stages. In Liuiiitus this similarity in body form is 

 very close, and the present paper shows how similar in essen- 

 tial features the behavior is in the two stages. 



. The single exception to the general rule of essential simi- 

 larity in type of behavior between adult and embryo in Limidus, 

 is found in the swimming movement. In the embryo the legs 

 take no active part in this movement, while in the adult they 

 beat synchronously with the gills. So far as the legs are con- 

 cerned we evidently have here a simpler type of behavior in the 

 embryo than in the adult. The holding of the legs in a cramped 

 position as described must be regarded as a definite action, just 

 as any movement would be, only it is simpler in character than 

 a rhythmical movement. The difference here in behavior be- 

 tween embryo and adult is without doubt associated with a 

 morphological difference in the nervous mechanism. 



In the case of swimming and walking movements, and the 

 righting reaction the study of the embryos give indubitable 

 evidence that there is improvement with practice. The embryo 

 performs these movements better — that is, with steadily increas- 

 ing purposiveriess — the more it practices them. At the time 

 of hatching it is endowed, so to speak, with an ability to per- 

 form certain acts, but is unable to perform them in such a way 

 that they serve any purpose at all well. The latter ability 

 comes with practice. Shall we call this "learning through ex- 

 perience" how to do certain things? It seems to the writer 

 that one who maintains that it should be so called will occupy 

 a practically impregnable position, yet he will be totally unable 

 to prove that this necessarily involves any psychical element. 



