Maech 12, 1909] 



SCIENCE 



431 



does so because the nematocyte enclosing it has 

 -been stimulated. 



Elevation of the internal pressure of the nema- 

 tocyst may be the cause of normal explosion in 

 •ccelenterates. If we suppose that stimulation of 

 the nematocyte inaugurates changes which result 

 in lowering the concentration of the cell contents 

 surrounding the nematoeysts, the result can be 

 understood. If, as is not unlikely, heat is liber- 

 ated, the matter becomes still easier, for either 

 -dilution or heat can separately bring about the 

 instantaneous discharge of freshly isolated nema- 

 toeysts. 



Distortion brings about the discharge of isolated 

 nematoeysts, but uniform external pressure is use- 

 less. It might be supposed that inside the nema- 

 tocyte there is a mechanism capable of squeezing 

 the nematocyst. Such a mechanism is at present 

 purely hypothetical, and, it seems to me, not 

 needed to explain the facts. 



The threads of nematoeysts, contrary assertions 

 •notwithstanding, are able to penetrate the tissues 

 •of other animals, but in order to do so must 

 make their puictures during the period of highest 

 speed, viz., at the beginning of the eversion. This 

 observation renders unnecessary the assumption 

 of a " Reizgift," made in order to account for the 

 nettling sensation produced by nematoeysts. 



The Behavior of the Cuokoo : Fbancis H. Heebick, 



Western Reserve University. 



There is no conclusive evidence to show that the 

 American black and yellow-billed cuckoos are 

 ■either losing their nesting instincts, or that once 

 having lost them they have been regained. Pos- 

 sibly a lack of attunement of the cyclical instincts 

 occasionally seen in all birds, and rather more 

 frequent in these cuckoos, may have been the start- 

 ing point of the " parasitic " habit of Guculus 

 ■ca/norus and related old-world genera. Parental 

 instinct is strong in the American cuckoos, and 

 their nests, though frail, are well adapted to their 

 .purposes. 



The eggs are commonly laid and hatched on 

 alternate days, but nest-life is not unduly pro- 

 longed in consequence, this apparent extension 

 being counterbalanced by the development of a 

 remarkable climbing instinct in the young and a 

 premature desertion of the nest. In the life and 

 ^behavior of the young cuckoo three stages are 

 •clearly distinguished : ( 1 ) period of infancy, when 

 their black skin is sprinkled with snow-white 

 "hairs" or rudimentary down; (2) complete 

 quill stage on the sixth day and (3) the climbing 

 stage when on the seventh day the nest is sum- 



marily deserted by each bird in order of develop- 

 ment, and marked by a sudden though incomplete 

 transition to the feather state. 



The cuckoo is remarkably enduring from birth, 

 and its grasping reflex most striking. When born 

 it can support its own weight with one foot or 

 with a single toe. Later with feet and bill it 

 easily raises itself upon any support. At the close 

 of the quill-stage fear is present, and there is per- 

 fect association with the nest and parent. The 

 feather tubes now begin to give way at their base, 

 especially over the breast and abdomen, and in the 

 energetic practise of the preening instinct the 

 tubes are combed off by the mouthful and in a 

 few hours. The tubes of the flight-feathers and 

 those of the back break away centripetally, so as 

 to expose the shafts gradually as in other birds. 

 When the bird climbs out of the nest early on the 

 seventh day it is only half fledged, quills still 

 showing on head, neck and back. In the climbing 

 stage, when they remain in bushes for upwards of 

 ten days, their behavior suggests that of the young 

 hoatzin. 



In serving the large caterpillars and larvae 

 which are brought to the nest by both parents, 

 the insect is placed in the mouth, and not in the 

 throat, as in nearly all birds observed, and is held 

 there for, it may be, five minutes, neither bird 

 moving, or until the swallowing reflex is started. 

 The last bird in the nest is apt to be deserted, 

 parental instinct being diverted and satisfied by 

 the attentions which those already in the bush 

 demand. 



Phototaxis m Fiddler Grabs: S. J. Holmes, Uni- 

 versity of Wisconsin. 



The Reactions of Amphibians to Light: A. S. 



Peaese, University of Michigan. 



Ten representative species of amphibians were 

 tested and all of them showed marked phototropic 

 reactions. In most instances these species gave 

 the usual responses after the eyes had been re- 

 moved, the skin serving as a photoreceptor. When 

 a toad was stimulated through only one eye by 

 light from in front or when the skin of an eyeless 

 toad was subjected to imilateral stimulation by 

 light from above, the resulting locomotion was 

 toward the stimulated side and not toward the 

 source of illumination. Such responses are, there- 

 fore, brought about by bilateral differences in 

 stimulation and not by any orienting influence due 

 to the direction of the light rays. Previous condi- 

 tions of light stimulation had no apparent effect 

 on the photic responses of the toad. 



Although the rays toward the ■violet end of the 



