Embryos and Nestlings of Centropus sinensis. 657 



between itself and the pt. spinalis an elongate narrow 

 apterium (see arrow in fig. 1 p. 655). At the knee the 

 pt. femoralis runs into the — 

 Pt. cruralis (fig. 2, pt. cr.), which is divisible into two por- 

 tions, a narrow pre-axial and a broader post-axial, which 

 again are confluent with each other in the lower third 

 of the crus on its outer aspect. 

 Pt. colli lateralis (fig. 2,pt. coll. lat.) is at present well defined, 

 though not recognizable in the adult or even in Stage 3 ; 

 it branches off from the pt. spinalis at the junction of 

 the head and neck, and runs obliquely on to the upper 

 part of the breast, where it becomes confluent with the 

 pt. ventralis. After its origin it is separated from the 

 pt. spinalis by the apt. colli laterale, which runs down as 

 far as the pt. huraeralis (it is found also in the adult), 

 and from its fellow of the opposite side by the naked 

 skin of the throat. The trichoptiles of this and the 

 following tract are very small. 



Pt. ventralis (Hg. 2, p. Qoo,pt.v.). — This is, as yet, merely 

 rudimentary, ami the rudiments are curiously disposed. 

 As is well known, the pt. ventralis in the genus Centropus, 

 after bifurcating, redivides again on each side into an 

 inner and outer branch. In the embryo now under 

 discussion, the | osterior end only of the inner branch is 

 seen running on each side from the lower part of the 

 stomach to the anus, and the upper part of the outer 

 branch extends from its junction with the pt. colli 

 lateralis to the level of the knee-joint only. 

 The oil-gland is not tufted, and there is no pt. ani. 



Pt. caudce (fig. 1, pt.caud.). — The ten rectrices and their 

 coverts are represented by short trichoptiles. 



Pt. alaris. — Owing to the small size of the fore-limb and the 

 disproportionately long trichoptiles, it is almost impos- 

 sible to make out their relative positions {cf. description 

 ot this tract in a nestling of Stage 2). 

 With the exce^jtion of the pterylosis, there is not much in 



the external features of this embryo to call for special notice. 



The egg-tooth is sir all but prominent; the nostrils are 



