Scientific Proceedings. 



19 



Third meeting. 1 



Zoological Laboratory of Columbia University. October 21, ipoj. 



13. " An experimental study of cell-specification in embryonic 

 development," with demonstrations : EDMUND B. WILSON. 



The author presented the results of a study of the de- 

 velopment of isolated embryonic cells, in the mollusks Patella 

 and Dentalium, which demonstrates that from the first cleavage 

 onward, an isolated blastomere undergoes essentially the same 

 differentiation as if it had remained in connection with its fellows. 

 These eggs accordingly show a true mosaic development and differ 

 widely in this respect from those of echinoderms. It was also 

 shown that the specific character of the cleavage cells is prede- 

 termined, at least in part, by specification of the regions of the 

 unsegmented egg from which the blastomeres arise, as is proved 

 by the development of fragments obtained by cutting the egg in 

 two before development has begun. 



14. " The occasional presence in the blood of untreated adult 

 animals of large amounts of substances agglutinating many 

 bacteria," with demonstrations : WILLIAM H. PARK. 



The affinities of bacteria for specific agglutinins have been made 

 use of, since the researches of Gruber, to establish relationships 

 between different cultures. The test properly performed is delicate 

 and reliable, but when carried out with insufficient precautions is 

 often misleading. It has been known for some time that the 

 blood of animals before immunization possessed, in moderate 

 amount, substances which agglutinated many bacteria. An agglu- 

 tination of bacteria must, therefore, take place in a high dilution 

 of serum before it can be considered a specific reaction. 



From results obtained in his own researches, the author con- 

 siders that even this requirement is insufficient. He found that, 

 before any inoculations had been made, the blood serum of certain 

 horses agglutinated, even in such great dilutions as 1 in 1,000, 

 both the bacilli having the characteristics of the true dysentery 

 bacilli of Shiga, and those having the characteristics of the mannit- 

 fermenting class of Kruse, Flexner and Duval. This was true to 

 a somewhat less extent of the serum of full-grown goats. It has 



1 Reprinted from American Medicine, 1 903, vi, p. 733. 



