EARLY PULSATIONS OF LYMPH HEARTS 381 



a change of temperature was delayed. In this case, when the 

 temperature was raised to 41° or lowered to 35°, the peristaltic 

 contractions ceased and the amnion relaxed, allowing the embryo 

 to sink deep into the yolk. The periodic movements persisted 

 for several minutes, in such instances, probably owing to the 

 more sheltered position of the embryo. 



The movements of fish and amphibian embryos in the egg 

 have been studied by many investigators. Preyer reviewed the 

 literature on the subject and published many new observations 

 on the embryos of the trout and the frog. He finds both active 

 and passive movements occurring in these embryos: the passive 

 movements are due to the almost continuous rotation of the 

 embryo inside the egg, caused by the action of the cilia. The 

 active movements, according to Preyer's description, resemble 

 greatly those present in chick embryos of four to five days, the 

 body bends from side to side and the head and tail bend at the 

 same time. More recently, Harrison, Hooker, Wintrebert and 

 Coghill have observed movements in early amphibian embiyos, 

 and Paton has studied them in embryo fish. No periodic move- 

 ments were noted by any of the investigators of amphibian mate- 

 rial. Mention is made of spontaneous movements, but as a 

 casual and not a frequent occurrence. Harrison distinguishes 

 two types of response to stimulation in young amphibian em- 

 bryos: (1) the non-nervous type, characterized by a sharp tonic 

 contraction and (2) the nervous type which resembles a swim- 

 ming movement. The former has been shown to be the more 

 primitive, since it is noticed in embryos before the peripheral 

 nerves have developed (Wintrebert) and has also been demon- 

 strated in embryos in which the spinal cord had been cut or 

 removed (Harrison and Hooker). It appears, then, that the 

 early movements of chick embryos differ from those noted in 

 amphibia, by occurring periodically and with greater frequency, 

 and also in the fact that they can not be instigated or altered by 

 mechanical stimuli, such as pressure or direct piercing of the 

 muscles with glass needles. 



The early movements of fish embryos, described by Paton 

 show a closer resemblance to the movements of chicks. In 



