ASYMMETRIC ANALYSIS 119 



isms in wliicli the laevo isomer of nicotine is more toxic 

 than the dextro- isomer. Tlie two groups correspond to 

 large divisions of the animal kingdom, and witliin each 

 division, there are hardly any exceptions. 



All the representatives of Protozoa, Coelenterata, Tur- 

 bellaria, Rotatoria and Nemertinea studied belong to the 

 first group. They are devoid of spatially specific recep- 

 tive substances in the process of poisoning by nicotine. 



It should be mentioned that the stereo-coefficients in in- 

 vertebrates are not atfected by the differences in the ab- 

 solute sensitiveness to nicotine, exhibited by various spe- 

 cies, as it has been noticed in vertebrates. Thus, for ex- 

 ample, Leptoplana is considerably more sensitive to nico- 

 tine than Procerodvs, but both these turbellarians are 

 characterized by an equal effect of the dextro and laevo 

 isomers. There are many other examples of the inde- 

 pendence of these characters. 



The lowest groups in the phylogenetic series, in which 

 a stronger eifect of the laevo isomer of nicotine is ob- 

 served, are the annelids, and particularly the Archian- 

 nelids {Saccocirrus), the Polychaeta and the Oligochaeta 

 and the primitive representatives of Deuterostomia {Sa- 

 gitta setosa). In Arthropoda (Crustacea and Insecta) 

 this etfect is absent, an equal toxicity of the dextro and 

 the laevo isomers is again observed. 



Let us now compare the stereo-coefficients in verte- 

 brates and in those invertebrates which show a higher 

 sensitivity to the laevorotatory nicotine. The following 

 values were recorded in invertebrates : 



Saccocirrus papillocerciis 



Perinereis cult rif era 



Pristina longiseta 



Limnodrilus Jiofmeisteri 



Helobdella stagnalis 



Nais communis 



Ch act og aster langi 



Aelosoma variegatum 



Aelosoma hemprichi 



Sagitta setosa 



Mean a 



