EARLY PULSATIONS OF LYMPH HEARTS 379 



In the third stage of development described by Preyer — the 

 period from the eleventh to the fifteenth day — the active move- 

 ments of the embryo continue to occur, at frequent intervals, 

 and, in addition to those present in younger chicks, movements 

 of the individual toes and opening and closing of the eyelids 

 and beak occur frequently. At this stage, reaction to mechani- 

 cal stimulation is doubtful : at times a seemingly definite response 

 is obtained and, at other times, the embryo remains motionless 

 when stimulated, although continuing to move spontaneously. 

 At this stage, however,, chicks responded definitely to electrical 

 stimulation, by movements of the limbs, toes, beak, etc., accord- 

 ing to the point at which the stimulus was applied. 



In the last period of development — from the sixteenth to the 

 twentieth day of incubation, Preyer states that spontaneous 

 movements are much less frequent, but that the chicks respond 

 readily to electric stimulation by tetanic contraction, and show an 

 increased tendency to respond reflexly to mechanical stimulation. 



With his especially constructed ooscope, Preyer was able to 

 observe, at all stages, both types of embryonic movements, those 

 due to the contractions of the amnion, and those due to con- 

 tractions of the muscles of the embryo itself, in the unopened 

 egg, kept at incubator temperature, thus proving that they are 

 normal, and not caused by outside factors introduced at the time 

 of opening the shell. 



Our observations of the muscular movements of chicks were 

 confined to embryos of four to fourteen days, since this com- 

 prises the important periods in the development and early fimc- 

 tioning of the lymph heart. Our observations agree with Preyer's 

 description of the character of these movements, and of their 

 first appearance in chicks of four days. However, in addition 

 to the movements of the various parts of the embryo, described 

 by Preyer, we noticed that sudden violent jerks, which seemed to 

 involve the entire musculature of the embryo, occurred at all 

 of the stages studied. With regard to the absence of all reaction 

 to mechanical stimulation, in chicks between the fifth and 

 eleventh day, our results are in entire agreement with those of 

 Preyer. 



