August 24, 1900.] 



SCIENCE. 



299 



of the Nectria were found to be abundant 

 on them. Professor Sears writes that this 

 form of canker is doing serious damage in 

 some of the orchards of the Annapolis 

 Valley. 



Specimens of the diseased branches were 

 sent to Dr. E. Hartig, Munich, Germany, for 

 identification, who writes that the cankers 

 are caused by the fungus Nectria ditissima. 



So far as I know this fungus has not as 

 yet been recorded as occurring on apple 

 trees in America, and its appearance in our 

 orchards is of great practical importance 

 since it is a serious pest to European fruit 

 growers. 



W. Paddock. 



ExPEEiMENT Station, Geneva, N. Y. 



ZOOLOGY AT THE ASIEBICAN ASSOCIATION. 

 The following papers were presented be- 

 fore Section F during the recent meeting at 

 New York : 



Sketch of the History of Statistical Inquiry of 

 Evohctio.n ■■ By C. B. Davenpoet, Univer- 

 sity of Chicago. The paper will appear 

 in full in Science. 

 The Variation of Synajita : By C. L. Ed- 

 wards, Trinity College. In the absence 

 of the author this paper was read by title. 

 Variation among Hyclromeduscs : By Charles 

 W. Hargitt, Syracuse, N. Y. To be 

 published in Science. 

 Variations in Jaws of Neries limbata : By 

 Marian Heffeean, University of Chi- 

 cago. Presented by C. B. Davenport. 

 A quantitative study of variation made 

 upon the species Neries limbata, collected at 

 Cold Spring Harbor during the summer of 

 1899, gave the following results : 



The character chosen for investigation 

 was the number of teeth on the exsertile 

 jaws. These number from 6-14 on each of 

 the two jaws and were distinguished both 

 for the sake of convenience and for pur- 

 poses of comparison into definite teeth. 



those which occupy the distal half of the 

 jaw and which are clearly separated from 

 each other, and the indefinite teeth at the 

 base of the jaw which are covered by a 

 transparent horny layer. 



The typical condition of the total num- 

 ber of teeth of 400 specimens of Neries lim- 

 bata of Cold Spring Harbor is a curve of 

 type I. or type IV. , with a slight skewness 

 in a negative direction from the mode 10. 

 In case of the calculation of the right total 

 teeth a transition from a curve of type IV. 

 to an equally serviceable one of type I. 

 could be made by dropping one extreme 

 individual out of 400. The teeth on the 

 right jaw appear to be slightly more vari- 

 able than those on the left. The least 

 variation is shown by the indefinite teeth. 

 The degree of correlation between the two 

 jaws is, on the whole, rather high, 0.820. 

 Correlation is closer between the indefinite 

 than between the definite teeth. A nega- 

 tive correlation exists between the definite 

 and indefinite of the same jaw, that is, a 

 small number of definite teeth is associated 

 with a large number of indefinite and vice 

 versa. An inverse relation also exists be- 

 tween the number of definite teeth and the 

 age of the animal, older animals presenting 

 fewer definite teeth. 



This result as well as those of observa- 

 tion of many specimens showing many ir- 

 regularities in the teeth, point to the con- 

 clusion that a process of erosion of the ex- 

 treme teeth forms a large factor in the 

 variation of the definite and perhaps indi- 

 rectly of the indefinite teeth. A difierence 

 in the number of teeth in respect to the age 

 of the animal has rarely been recognized in 

 description heretofore and would be natur- 

 ally overlooked unless a large number of 

 specimens was examined. Little value can 

 thus be placed upon the statements made 

 in regard to the number of teeth in a large 

 number of species where only a few speci- 

 mens were found. 



