1 62 O. C. GLASER. 



ingested ova. It might be urged from this that there is not even 

 an indirect connection between the cannibalistic habit and the 

 excretory organs, but this is by no means true. It is an acci- 

 dent in the lives of the dwarfed embryos that they fail to secure 

 any eggs, for they prepare for them as much as their more suc- 

 cessful competitors do. The fact that the preparations for an 

 event which never comes to pass are elaborate cannot show that 

 this event had no influence on the lives of the anticipators. 

 What it does show is that this influence is not direct, for the 

 habit of preparing for cannibalism has become fixed through 

 selection. 



Another correlation of importance is the amitosis in the exter- 

 nal kidneys and in the oesophageal endoderm. Here the need 

 for the rapid digestion of great quantities of food material and the 

 excretion of waste products has called forth a process unusual in 

 embryonic cells, but, as I shall try to show in another paper, not 

 pathological. There can be little doubt that through these ami- 

 toses other correlative changes are brought about, particularly in 

 the development of the oesophagus, where the gaps made by the 

 degenerating embryonic digestive cells are certainly repaired 

 before the adult stage has been reached. Thus the whole devel- 

 opment, from early stages to late, the structure, shape and size 

 of the larvae and the size and hardiness of the young, and what- 

 ever these stand for in their further lives, are affected by cannibal- 

 ism, the origin of which is traceable, I believe, not to the advan- 

 tage which accounts for its persistence, but to some as yet 

 unknown cause which determines the existence of the sterile 

 nutritive ova. 



ZOOLOGICAL LABORATORY, UNIVERSITY OF MICHIGAN, 

 ANN ARBOR, January 4, 1906. 



LITERATURE CITED. 

 Blochmann, F. 



'82' Uber die Entwicklung der Neritina fluviatilis. Zeit. f. w. Zoo]., Bd. 

 XXXVI., 1882. 



Bobretzky, N. 



'77 Studien iiber die embryonale Entwicklung der Gastropoden. Arch. f. mikr. 

 Anat., Bd. XIII., 1877. 



Brooks, W. K. 



'78 Preliminary observations upon the development of the marine prosobranchiate 

 Gastropods. Chesapeake Zool. Laboratory, Johns Hopkins Univ. Scient. 

 Results, 1878. 



