56 



iiolliiiii;' is known on llic time at wliicli llic resistance 

 drops. Moraii (liJ'J.")) remarks in a general maiiiior that 

 l)artiall\" incnhalcd ej;g'.s were less resislaiil lliau i'resli 

 eggs to low-tenipcialni-e storage. According to Edwards 

 (J. PJii/.sioI., li, M.")!, 11)02), cliick euiJjryos responded like 

 cold-l)lo()de(l animals to temperature cliauges diii'ing tlie 

 lirsl 20 days of ineiil)atioii. This statement would indi- 

 cate a very late change in resistance. 



On the more fundamental problem of the mechanism 

 of the decrease in cold resistance during incubation, as 

 related to the mechanism of the passage from the poikilo- 

 therm to the honioiotherm state, still less is known. 



3. Ciliated EpifJu'lium. According to Schiff ("Lehrb. 

 d. Physiol, d. IMenschen," 1, VI, 1858), a ciliated frog epi- 

 thelinm, immersed for several hours in iodine serum at a 

 few degrees above zero and bronght into a warm room for 

 observation, presented a complete absence of movement; 

 but, with rising temperature, a slight motion began which 

 was soon followed by an intense ciliary activity. This 

 experiment could l)e carried out repeatedly on the same 

 preparation. 



Koth [Arch. f. path. Anaf. u. Physiol., 87, 188, 1866) 

 made more accurate determinations of the temperature 

 of cessation of ciliary motion in Anodonta. The experi- 

 mental object, with a thermometer and enough water to 

 cover the bulb of the thermometer, was placed into a re- 

 agent glass, and this was set into an ice-salt mixture. 

 Recovery w^as found possible after congelation at - 3° to 

 - 4°, when this temperature was not maintained for more 

 than a few minutes. At - 6°, death always set in. Tem- 

 peratures above zero, w^hen they acted long enough, pro- 

 duced a transient cessation of motion; this happened, for 

 example, at 0.4° after 6 minutes. By freezing and tliaw- 

 ing, the endosmotic relations of the ciliated cells were 

 extraordinarily changed; the movement, temporarily re- 

 sumed, was soon definitely lost, and the cells sw^elled up; 

 very often the cuticle, with the cilia attached to it, sepa- 

 rated from whole cell rows and sometimes it rolled up 



