Febeuaby 16, 1900.] 



SCIENCE. 



253 



Variation in the sea anemone Sagartia Lucioe. 



Gertrude C. Davenport. 



Sargartia Liicim is conspicuously marked 

 by a varying number of orange colored 

 bands which run longitudinally. These 

 orange bands were counted in 751 individ- 

 uals at Cold Spring Harbor. Their number 

 varied from 0-20. The largest proportion 

 had 12 stripes. Secondary maxima occurred 

 at 8, 4, 1 and 16. Longitudinal division 

 was observed in which the twelve stripes 

 were apportioned to the two resulting in- 

 dividuals as follows : 9-3 ; 4-8 ; 5-7. Also 

 such divisions as 3-3 ; 7-1 were noted. 

 Hence the variation in the number of stripes 

 is dependent upon fission. Division, so far 

 as observed, was aboral-oral and was usually 

 accomplished within of 24 hours. By feeding 

 to repletion, division already begun could be 

 delayed, even apparently prevented. When 

 cut longitudinally into halves regeneration 

 was rapid. Even small fragments artificially 

 obtained reproduced normal individuals. 

 Normal division was observed only in di- 

 glyphic types. Monoglyphic individuals arp 

 plentiful and occur as the result of division of 

 diglyphic forms. Basal budding and frag- 

 mentation are believed to be very common 

 method of multiplication of this species. 



Variation studies on Pectinatella magnifica. 



C. B. Davenport. 



The number of spines on the statoblasts 

 of Pectinatella from Chicago was counted in 

 over 800 cases. The. law of distribution of 

 frequencies was deduced by quantitative 

 methods. The skewness is positive, that is 

 there is an excessive tendency toward large 

 numbers. This fact of variation in the form- 

 unit agrees with the fact that the other races 

 of Pectinatella magnifica and the other species 

 of the genus have a larger modal number of 

 spines. The ontogenetic causes of the vari- 

 ation and of abnormalties was considered. 

 C. B. Davenport. 



Secretary. 



SOME OF THE PROBLEMS OF LIMNOLOGY* 

 If the object of science is to correlate and 

 state the results of observation in such a 

 way as to produce mental economy, it can 

 hardly be said that limnology has developed 

 very far as a science. It is certainly still 

 true that much of our knowledge regarding 

 lakes is in that condition of detailed state- 

 ment whose mastery involves great mental 

 exertion. Through this stage all sciences 

 have passed and signs are not lacking that 

 limnology will soon reach the position now 

 occupied by older branches of biological 

 science. To secure this result the student 

 of lake life must attempt to solve problems 

 rather than merely to state facts. 



Two classes of problems present them- 

 selves to the limnologist : the first, scien- 

 tific; the second, practical. The first com- 

 prises the problems raised by the study of 

 the lake as a unit of environment. The 

 second class concerns itself with the ques- 

 tion of the lake as a unit of economic pro- 

 duction. The answer to the practical 

 question depends on the correct solution 

 of the scientific problems. 



In attempting to solve these problems the 

 limnologist finds himself constantly ham- 

 pered by the lack of knowledge through 

 which he may interpret the results which 

 he reaches. The acquirement of this knowl- 

 edge seems to me the first and most neces- 

 sary step toward bringing exactness and 

 comprehensiveness into our views of lake 

 biology. We count the constituents of the 

 plankton, but are not able to state the sig- 

 nificance of the results which we reach. 

 Laborious and slow as the process of count- 

 ing is, I see no escape from the conclusion 

 that it will remain for a long time the only 

 exact way of ascertaining the facts regard- 

 ing the assemblage of plants and animals 

 which constitute the plankton. For the 



* Address in opening discussion on ' Methods and 

 Results of Limnological Work, ' at the meeting of 

 Naturalists at Chicago, December 28, 1899. 



