Apeil 21, 1911] 



SCIENCE 



629 



until to date (February 8, 1911), showing only 

 a slight trace around the inner part of the 

 core. 



It is interesting to note that early in the 

 season several normal fruits were injured by 

 passing a sharp instrument through them 

 from side to side and allowing them to remain 

 on the tree for 48 hours thereafter. A section 

 was then made through the injury and the 

 guiacum solution applied. The blue color de- 

 veloped first quite strongly around the walls 

 of the injury, followed gradually by the other 

 parts of the pear. 



From the preceding it will be readily seen 

 that there exists in the normal living fruit 

 two enzymes, a catalase and an oxidase. The 

 latter is probably most abundant in the early 

 part of the season, gradually decreasing in ac- 

 tivity as the fruit approaches maturity and 

 ripens. Furthermore, from the above results 

 it appears that tannin as such does not exist 

 in any part of the normal, uninjured fruit 

 previous to maturity, except possibly a small 

 amount in the peel, but exists as a poly-atomic 

 phenol, which upon injury is acted upon by 

 the oxidase and forms a tannin or tannin-like 

 body having the property of precipitating* 

 proteid matter, and at the same time forming 

 a germicidal fluid. This oxidase acts only in 

 an acid solution, and when present in an 

 amount above a certain undetermined mini- 

 mum. The above conditions are always pres- 

 ent in normal immature pomaceous fruits. 

 When normal, immature fruits are subjected 

 to injury by fungi, insects, or mechanical 

 agencies, the action of the oxidase on poly- 

 atomic-phenol is brought about with the ef- 

 fects as stated above. 



Mel T. Cook, ' 

 H. P. Bassett, 

 Firman Thompson, 

 J. J. Taubenhads 

 Delaware Agricultural Experiment Station, 

 Newark, Delaware. 



THE relation of PERMEABILITY CHANGE TO 

 CLEAVAGE, IN THE FROG's EGG 



Unfertilized eggs (taken from the uterus) 

 of the wood frog, Rana sylvatica, were caused 



to assume the normal orientation in the jelly, 

 and to segment, by electrical stimulation. 

 An alternating current of 60 cycles and 110 

 volts was passed through the tap water con- 

 taining the eggs, from platinum electrodes 

 about two inches apart. Stimulation for one 

 second seemed to give the best results. The 

 eggs were placed in fresh water immediately 

 after stimulation. 



Similar eggs were caused to segment by 

 mechanical stimulation, even while the jelly 

 remained intact. However, the most reliable 

 mechanical means of inducing cleavage was 

 found to be Bataillon's method of pricking the 

 egg with an extremely fine needle. The first 

 cleavage furrow often passed through the 

 point of puncture. 



Thousands of eggs were operated on. Con- 

 trol eggs were kept to both sets of experiments, 

 and showed no segmentation or rotation within 

 the jelly. 



The following indirect evidence is given to 

 show that a change in permeability is asso- 

 ciated with both of these means of inducing 

 cleavage : 



1. These " stimuli," if applied in greater in- 

 tensity or duration than is necessary to pro- 

 duce cleavage, result in rapid osmotic ex- 

 change with the medium and death of the egg. 



2. Similar electrical and mechanical " stim- 

 uli " produce segmentation in the sea-urchin's 

 egg, a process which I have shown to be pre- 

 ceded by an increase in permeability. 



With the exception of the rate of oxidation, 

 this change in permeability is the only known 

 coiamon intermediate step between fertiliza- 

 tion or artificial " stimulation," on the one 

 hand, and cleavage on the other. Further- 

 more, there is indirect evidence to show that 

 increase in permeability is associated with 

 fertilization, in the frog's egg, as I have shown 

 to be the case in the sea-urchin's egg : Back- 

 man and Eunnstrom' observed that, whereas 

 the osmotic pressure (freezing point lowering) 

 of the ripe ovarian egg of the frog is the same 

 as that of frog's serum, the osmotic pressure 

 of the fertilized egg is the same as that of the 

 pond water in which it lies. Since the frog's 



^Bioohem. Zeitschr., 1909, XXII., 390. 



