146 Journal of Comparative Neurology and Psychology. 



hindrances are great enough to overbalance the weight of the 

 embryo, the latter will turn over within the sphere. 



In the movements of translation of the eggs as a whole 

 the direction of the movement is usually such as to keep the 

 abdomen of the embryo in advance. This is a mechanically 

 necessary result if the movements are produced in the manner 

 just described. Of course, circumstances will sometimes pre- 

 vent the egg from moving in a perfectly straight line, and again, 

 the pressures exercised by the legs on the two sides of the body 

 are not equal in amount. That they are about equal in the 

 long run is shown by the fact that in the great majority of cases 

 when free movement of the egg for some distance occurs, this 

 movement is very approximately in a straight line. In cases 

 where the movement is somewhat irregular the longitudinal axis 

 of the embryo may not lie exactly in the path of motion, yet 

 in no case have I ever seen the anterior end of the embryo in 

 advance in the free translatory movements of the ftg^. The 

 movements are always either somewhat sidewise with reference 

 to the embryo, or, much more commonly, with the abdomen 

 in advance. 



In the behavior just described there is no definite co-ordi- 

 nation in the movements of the legs. Each leg acts by itself. 

 and there is no rhythmic order in which the different legs move, 

 as is the case, for example, in the gustatory refiexts of the 

 adult Livmlns (cf. Patten, '93, pp. 7-9). 



The behavior when the "vicarious chorion" is held so that 

 it cannot move offers some points of interest. The embryo is 

 seemingly unable to maintain itself with the haemal side upper- 

 most even after it attains that position in the manner described 

 above. This is apparently a consequence of the fact that the 

 organism after getting into the upright position does not stop 

 the movements of the legs. When the legs are extended with 

 the animal in an upright position the whole body is of course 

 raised till its haemal surface is nearly in contact with the 

 uppermost part of the sphere. When the embryo is in this 

 position, if the effective pressure of the legs becomes greater on 

 one side than on the other, as invariably happens, it forthwith 



