AVIAN GENUS CHRYSOCOCCYX 67 



The characteristics of the egg shells, coloration, size, gloss, and 

 porosity, etc., are not necessarily simple to explain in an adaptive- 

 evolutionary sense, since they may have come about in more ways 

 than one. Furthermore, egg shells of brood parasites seem to be 

 unusually subject to natural selection and consequently are relatively 

 unreliable indications of past events or of interspecific relations. 

 Thus, one species of parasite may have begun with an originally 

 broad range of egg variability and later may have developed special- 

 ized egg morphs, uniform for each individual hen and each specific 

 on a single species of fosterer, while another may have begun Anth a 

 constant, or only narrowly variable, egg pattern. In the latter case, 

 the parasite may have remained with a smgle egg type and may have 

 come to select hosts with fau'ly similar eggs, or it may have developed 

 a broader range of coloration than it had originally. Unfortunately, 

 in no case can we claim to know with any finality which course was 

 followed. All that we can do is to describe the present situation in 

 each of the nine species and see if there are any clues or suggestions 

 as to trends, past conditions, or appreciable, inferential, evolutionary 

 changes in them, and, in addition, to see if together they yield any 

 hints of theu' history as a group. 



In our attempted reconstruction of the phylogeny of the species 

 of the genus Chrysococcyx we have already seen that the African 

 members of the group are markedly different from the Asian and 

 Australian ones. The gap, both in morphological characters and in 

 geographic distribution, that separates them from their eastern 

 relatives is the largest void in the phylogenetic picture. It is pertinent 

 at this time to point out that there is a correspondingly great differ- 

 ence in theu" eggshell characters as well. The eggs of three of the four 

 African species (caprius, cupreus, and Haas, the eggs oi jiavigularis 

 being unknown as yet) are far more variable within each species — 

 actually polymorphic — than are the known eggs of the southern 

 Asiatic and the Australasian species (basalis, lucidus, maculatus, 

 malayanus, osculans, and xanthorhynchus) . Some of the latter, of 

 whose eggs sufficient numbers are known to give a trustworthy 

 picture, are remarkably uniform, as, for example, basalis, lucidus, and 

 osculans. This seems to be the case, although with less supporting 

 evidence (smaller yet sufficient numbers of eggs) in malayanus, but 

 not in maculatus and xanthorhynchus. 



The degree of variability of the eggs, chiefly in their coloration, 

 ranging from a monomorphic to a polymorpliic condition, is not ob- 

 viously related to, or correlated \\dth, the diversity and the number 

 of kinds of hosts used regularly. Thus, the species of glossy cuckoos 

 with very extensive lists of hosts include basalis and lucidus — each 



