Literar)' Notices. Ixxxv 



Habits of Warblers.' 



Dr. J. Lowe gave an account ( Linnean Society, June i) of a 

 newly-observed habit of the blackcap, Sylvia atricapilla, in puncturing 

 the petals of certain flowers ( Ilebiscus Rosa-sinensis and AbuHlon 

 frondosum), specimens of which he exhibited, thus causing the exuda- 

 tion of a viscid secretion which proved attractive to insects upon 

 which the bird preyed. The observations in question were made at 

 Orotave, Teneriff, during the month of March last. 



Amitotic Cell-Division.^ 



The latest of Professor Frenzel's papers is a very careful study of 

 the histology of the mid-intestine of the crayfish which seems to afford 

 strong proof of his previous claim that the substituting cells, i.e. those 

 which are periodically formed to take the place of the rapidly decom- 

 posing ferment cells, are produced by a subdivision of mother cells 

 without karyokineses. 



The question as to whether it is possible for cells to multiply 

 otherwise than by means of the wonderful process of mitosis has long 

 been mooted and seems to develop a great deal of needless acrimony 

 in its discussion. The plates accompanying the paper are drawn with 

 painful acuracy and most scrupulous care as we have had personal 

 opportunity to know. The peculiar difficulty in this instance grows 

 out of the possibility of optical illusion in the case of cells which may 

 have their axes inclined to each other and to the plane of section, 

 thus throwing the nucleus into unexpected juxtaposition and making 

 it hard to determine whether they belong in a single cell or in two 

 adjacent cells. 



Professor Frenzel concluded with the generalization that in in- 

 vertebrates there are two distinct methods of cell production ; first, 

 cell-increase, always by mitosis, occuring in cases where the organ or 

 part is in actual growth ; second, cell-renewal or regeneration, a pro- 

 cess which occurs in the amitotic manner. 



This problem is germam here in so far as it indirectly strengthens 

 a tentative suggestion made several years ago that in certain parts of 

 the brain cell increase continues late in life where mitosis cannot be 

 demonstrated. Especially is it apparent that in various parts of the 



'^Nature, June 15, 1893. 



^Frenzel Johann. Die Mittledarmdriise des Flusskrebses und die ami. 

 totische Zelltheilung. Arch. f. Mikrosk. Anatomie XLI. 3. 1893. 



