ZOOLOGY: C. ZELENY 
211 
their accumulation to the bringing of vegetable material from elsewhere 
by air and by water transport. It follows that the commoner coals 
have had a similar derivation since they have practically an identical 
organization. 
It may be summarily stated in conclusion, that there is no good 
evidence that 'coal balls' are organized from material accumulated in 
situ. The facts that they often include isolated masses of charred 
vegetable matter and that identical material to that composing their 
substance is often accumulated under modern conditions, by transport 
and sedimentation in open water, furnish very strong evidence of their 
formation from transported material. Further the coals in which 'coal 
balls' have been found are abnormal coals singular by the absence of 
spore material which is a striking feature of the organization of typical 
coals of every geological age and all geographical regions. The struc- 
ture of the coals containing the 'coal balls' cannot consequently be used 
as an argument in favor of the in situ origin of coals in general, even if 
it were proved that they themselves had been accumulated in this 
manner, which, as has been shown above on the basis of the organiza- 
tion of 'coal balls,' is very far from being established. The great mass 
of coals by their close resemblance in organization to cannels show 
that they have been laid down under the open water and transport con- 
ditions, which are universally conceded for the coals of the canneloid 
category. A fuller account with evidence in greater detail will appear 
at a later date. 
1 Jeffrey, E. C, Economic Geology, 9, 1914, (730-742). 
2 Jeffrey, E. C, Chicago J. Geol. Univ. Chic, 23, 1915, (218-230). 
3 Jeffrey, E. C, Science Conspectus, Boston, 6, 1916, (71-76). 
4 Stopes and Watson, London Phil. Trans. R. Soc, B. 200, 1907, (167-218). 
THE EFFECT OF DEGREE OF INJURY. LEVEL OF CUT AND TIME 
WITHIN THE REGENERATIVE CYCLE UPON THE RATE OF 
REGENERATION 
By Charles Zeleny 
DEPARTMENT OF ZOOLOGY. UNIVERSITY OF ILLINOIS 
Communicated by E. G. Conklin, January 22, 1917 
1. Degree of Injury. — In a former series of papers the writer gave the 
results of experiments on the effect of degree of injury upon the rate of 
regeneration. A number of different species of animals and various 
combinations of injuries were involved. The results obtained tend to 
show that on the whole, within certain limits, the rate of regeneration 
