LANIIDAE. 



were spotted red; he ascertained, moreover, from the proportion of a 

 large number of clutches, that the erythristic eggs (laid, according 

 to Naumann's opinion, by old female birds, and largest in number) do 

 not exceed the others in numerical strength. The fact, referred to 

 by Thienemann, the Nestor of scientific oology, that he scarcely 

 ever received other than reddish collurio eggs from Dalmatia, does 

 not tend to confirm this transition hypothesis, either. It would 

 appear to me to be more probable — as I also assume to be the 

 case, for instance for Cuculus canorus — that the cullorio individ- 

 uals belong to oologically differentiated „tribes" (gentes), of 

 which, therefore, each has its own type of egg (not to be confused 

 with variety). 



For collurio I assume the existence of two such tribes; within 

 each tribe we see a limited variation in intensity of the shell pigment 

 proper to the type of egg. 



The distinctions between the two types which I have classified 

 are the following: 



I. Colour of shell: varying from whitish to sea green. (The comming- 

 ling of oocyan with carbonate of lime (-f- keratin, an albuminoid) in var- 

 ying proportions; oorhodein being wholly or almost wholly absent). 



II. Colour of shell: varying from light cream-colour to reddish. 

 [Oorhodein, commingled in varying proportions with carbonate of 

 lime occurring strongly predominantly as against oocyan). 



The question as to how far within each type the intensity of the 

 colouring and marking of the shell is dependent on the age of the 

 female birds, or whether influence is exercised thereon only, or also, 

 by food and climate, is an open one. 



The explanation given by Hocke for the occurrence of erythrism, 

 to the effect that it can arise from an exceptionally favourable 

 condition of well-being of the individual birds, appears to me to 



