OF THE TONGUE OF PAEEOTS. 



243 



stage, which constitutes the fourth one, to the next is somewhat sudden, since in Stage 5 

 the whole of the remaining portion of the muscle has returned to the parahyal process. 

 In the final stage, owing to the formation of a completed parahyal arch, by the growth 

 forwards and meeting in the middle line of the parahyal processes, with the formation 

 of a median symphysis, the hypocleidium, the muscle arises not from the crura, but 

 from the hypocleidium. 



It may be objected that the interpretation of the facts represented in Stage 4 implies 

 that the origin from the parahyal process is at once the most specialized and the most 

 primitive condition. Such an objection would be quite valid were it not that other 

 facts in the lingual myology support the conclusion arrived at by the consideration of 

 those relating to the thyroglossus ; and, moreover, there is a difference between the 

 two stages with respect to the insertion and the general course of the muscle in relation 

 to the thyrohyoideus {cf. ante, p. 241). If we arrange in two columns those Parrots 

 in which the thyroglossus arises from the parahyal process — in one column those which 

 my interpretation of the facts lead me to regard as primitive, and in the other those 

 which I regard as specialized — the divison will be as follows : — 



I. 



II. 



Primiti-ve. 



Specialized. 



1"| s"^] 



tg £. 3 5 ^ Coracopsis. 



Eos. 



rf- 1— t 



•' Psiitacus. 



Vini. 



tA 



Stringops. 



Lorius. 





Cacatua alba. . 

 „ iriton. 



Caica. 

 Cyanorhamphus. 



If 



Nasitenia. 



Nymphictis. 



^Cahjptorhynchus. 



Platycercus and some other 





members of Stage 6. 



Now a glance at the table of characters (pp. 266-269) of the inferior ceratoglossus 

 will show that those Parrots in which I regard the parahyal process origin of the 

 thyroglossus as secondary (column II.), and as distinct from those in which I regard 

 it as primitive (column I.), are, in virtue of the characters of that muscle, very much 

 speciahzed : some of them, in respect of the tendon and the amount of retrogression of 

 the ceratoglossus inferior anticus, are more advanced than others, but all of them have 

 reached their fullest development with regard to the extension posteriorly along the 

 hypobranchial of the ceratoglossus inferior posticus. It is very different, however, 

 with the inferior ceratoglossus of those Parrots arranged in column I. : four of the 



VOL. XVI. — PART V. No. 5. — October, 1902. 



2i\ 



