100 MR. W. K. PARKER ON THE STRUCTURE 



In this newer work the forms of the Fish and the Reptile have heen hefore my eyes 

 night and day. These have been to me as the larval and pupal stages through which 

 may he traced the changing materials out of which that vertebrate imago, the Bird, 

 is constructed, its hot blood infusing new life and producing unlooked-for trans- 

 formations. 



Now that cranial morphology is beginning to embody itself in a clear and intel- 

 ligible shape, it may be well to explain the meaning of certain terms that will of neces- 

 sity be in frequent use. 



The term metamorphosis I use in exactly the same manner and for the same purposes 

 as the entomologist, namely, as describing the whole series of changes undergone by the 

 skull or skeleton throughout the life-history of the individual. 



The borrowed term- isomorphic is used, in a zoological sense, for very similar types in 

 quite distinct groups : the Sun-birds (" Nectariniidae ") may be said to be the isomorphs 

 of the Humming-birds (" Trochilidse "). 



The term symmorphic may be used for any morphological part or parts in one type 

 which agree in their structure and development with those of some other types ; thus 

 the " Desmognathous " palate of the Parrot and that of the Goose are symmorphic ; such 

 agreeing structures are also said to be homologous or representative. 



Professor Huxley, in his paper (pp. cit. p. 454), places the Goatsuckers and Humming- 

 birds with the Passerine types, supposing them to have the true " iEgithognathous " 

 palate. This is an error : they are Insessorial Schizognaths. 



The Woodpeckers (" Picidae," p. 448) had this service done to them, namely, their vomer 

 was shown to be double, and their maxillaries to have a very rudimentary palatine plate. 

 Thus they could not be treated of as belonging to the Cuckoo tribe (" Coccygomorphse "). 



The palatal structures (trabecule, pterygo-palatines, and nasal capsules) of the Wood- 

 peckers show that these birds can be classified with none of the groups established by 

 Professor Huxley, as their face is intensely Lacertian and even Ophidian. I have there- 

 fore called this group of birds the " Saurognathae " (Trans. Linn. Soc, Zool. pt. 1, 

 1875, pp. 1-22, Plates I.-V.). 



That peculiarity of the Bird's face which has been termed " iEgithognathous " will be 

 explained. It exists in all the " Coracomorphae " and, besides these, in the Swifts, or 

 " Cypselomorphse " (op. cit. p. 468). 



The importance of the fact that a low, superstruthious bird like the Hemipod should 

 offer itself as a stock (" phylum ") to the half myriad of known Passerines cannot be 

 easily overrated *. 



My principal reason for describing the types of skull presented here is not zoological 

 but morphological. I wish, in some degree, to fill up that which remains over of cranial 



* On the distribution of " Alectoromorphse," see Huxley, Proc. Zool. Soc. 1868, pp. 294-319. The Tinamous 

 stand with one foot in that group and with the other over the struthious border, and the larger " Cracidse " (Crax 

 rjlobicera) and " Megapodidse" (Megacejphalon maleo) are "Desmognathous" (see Huxley "On Classification," p. 423, 

 for a figure of the former). Thus the Powl tribe sweeps over a huge zoological space, immediately overlying the 

 stratum occupied by the " Ratitse." Amongst the ancient extinct forms of this group we must look in imagination 

 for the forefathers of the Birds of Prey, the Climbers, and the Perchers. 



