

AMERICAN MICROSCOPICAL SOCIETV 

 ECOLOGICAL SUCCESSION OF PLANTS AND ANIMALS / 3 



Shelford i Biol. I'.ull.. her.. KM i \ concludes a series of papers 

 dealing with the biological succession in ponds at the head of Lake 

 Michigan. The following are some of the conclusions reached by 

 the author as the result of this series of interesting studies : 



1. The quantity of bacteria, plankton, vegetation, and large ani- 

 mals increases with the age of the pond. 



2. Terrigenous bottom and oxygen content decrease with the 

 age of the pond. 



3. Fish tend to adapt themselves to the type of food rather 

 than to become distributed or furnish successions in accordance with 

 the type of food. They are not necessarily most abundant where 

 food is greatest. 



4. Small oxygen content of older ponds will account for ab- 

 sence of fish from them. 



5. Conditions outside the breeding season are probably less im- 

 portant than those of this season in determining the success of fish. 



6. The conditions most favorable to the normal feeding of fish 

 are not only different from those most favorable to breeding, but are 

 even antagonistic ; and the former tend to encroach on the latter. 

 ment, and the preservation of balance between the breeding condi- 

 tions and the adult life-conditions. 



7. Animal succession in ponds is due to an unused increment 

 of excretory and decomposition products which causes increase in 

 vegetation ; a decrease in oxygen at the bottom ; and a general change 

 in the conditions affecting breeding. 



8. Succession of particular species, rather than the continued 

 dominance of some when they once become dominant, results from 

 the inflexibility of their standards of demands in accordance with 

 the changing conditions. 



CHROMATIC REDUCTION IN CELL DEVELOPMENT 



ihde fZeit. Wiss. Zool.. 1911) undertakes to showL-tfeat~\a 

 marked clTafarteristic of the (lifferentiatiojr^^-rnSfunng of cells is 

 the reduction of chro^latSB^Hthe^uicleus. He suggests, as illus- 

 trative of trris j --a-'snes with bacte?hr-ftt_Qne end and the red blood- 

 cells of^fiammals at the other. The bacteriaTie-scajfiiders as prac- 



