236 MJ{. G. V. MUDGE ON THE MYOLOGT 



when as an incorporate part of" the thyrohyoideus it arose from the apex of the 

 parahyal process, opposite to the insertion of the sterno-hyoideus, the extremities 

 of the two muscles were more or less confluent, as tliey are actually in Coimnis 

 holochlorus {infra, p. 240) ; when tlie tliyroglossus began to separate from the thyro- 

 hyoideus and to give up its origin at the parahyal process, it is probable that it carried 

 forward with it a portion of the sternohyoideus. 



Chrjjsotis viridigena stands on the borderland betvA'een stages 2 and o. The muscle 

 is similar to that in Chrysotis ochrocephala, but its free extremity is connected to the 

 middle part of the inner surface of the entoglossum, not by tendon or a prolongation 

 of its own substance, but by a definite tract of connective tissue ; this tract foreshadows 

 the actual growth forwards of the muscle itself to the entoglossum, such as has 

 occurred in stage 3. 



Method B. 



Stage 1. 



Coracopsis vasa is the sole representative of this stage by this method. The thyro- 

 glossus (PI. XXVII. fig. 17, th.g.) is separated from the thyrohyoideus along its whole 

 length ; but the course of the two muscles is coincident, their origins and insertions 

 are almost the same. An earlier stage, i. e. one in which the thyroglossus is more or 

 less confluent with the thyrohyoideus (only partially separated from it), is not represented 

 in this method. But in view of the mode of origin of the muscle by Method A, and 

 of the intimate relations of the two muscles here, we are justified in the assumption 

 that the thyroglossus of Coracopsis has arisen in the same way, by becoming split ofi" 

 from the thyrohyoideus. But iu this instance the separation of the two muscles has 

 been completed, and yet the old origiii at the parahyal process is retained. 



Stage 2. 



In Stringops (PL XXVII. fig. 18) the muscle is similar in its relations to the thyro- 

 hyoideus to that in Coracopsis, but it gives off a very small twig (th.g^.) from its inner 

 side, which is confluent at its extremity with a forwardly directed twig of the stylo- 

 hyoideus and with the extremity of its fellow of the other side. Stringops thus exhibits 

 the first beginning of stage 2, i. e. the gradual rejection of its primitive origin after the 

 splitting off of the muscle from the thyrohyoideus. Tlie connection of the twig with 

 the sternohyoideus is probably accidental and due to the same cause as the somewhat 

 similar arrangement in Chrysotis pjanamensis {ante, p. 235). In Psittacus (PL XXVII. 

 figs. 15 & 16) the muscle is like that in Stringops, but the internal twig {th.g'^.) is much 

 larger and nearly as large as the body of the muscle, and there is no connection with 

 the stylohyoideus ; thus its recession from the primitive origin has progressed to a 



