200 DR. T. S. COBBOLD ON ENTOZOA. [Ft'b. I, 



avian stock as an independent offshoot at much the same time as did 

 most of the other important families. It may be fairly asked what 

 reason there is for the assumption that there was a sudden break up 

 of the bird- type at any particular period. It appears to me from 

 the study of anatomy that this was the case ; and it is evident that 

 the acquisition of wings by the previously terrestrial type form must 

 have suddenly interpolated a large number of intruders into domains 

 already occupied, and must have all at once called forth a new aerial 

 struggle for existence, which, from the generalness of its action 

 must, within a short time, have brought out a great number of special 

 characters by natural selection. 



EXPLANATION OF THE PLATES. 

 Plate XII. 



Fig. 1. Provent riculus and gizzard of Chuuna derbiana, cut open, and part of 

 the front wall removed. 



2. Anterior view of lower portion of windpipe of C. derbiana. 



3. Back view of same, the muscles of the left side having been removed. 



4. Right side view of same. 



5. Portion of right coracoid bone (c) with coraco-brachialis longus (c.b.l) 



and coraco-brachiaMs brevis (c.b.b.) in situ, of Crax globicera. The 

 expansor secundariorum (e.s) is seen to spring partly from the first-- 

 named muscle. 



Plate XIII. 

 Fig. 1. Cffica of Chauna derbiana, with the anterior wall partly removed to show 

 the cavity intervening between the small and large intestine into 

 which the caeca open. 

 2. The caeca, external view. 



Plate XIV. 

 Fig. 1. Axillary muscles of right side of Chauna derbiana. e.s, expansor 

 secundariorum; p 1, great pectoral; p2, second pectoral; c.b.l, 

 coraco-brachialis longus; b, biceps; t, triceps; t.p.b, tensor patagii 

 brevis; sc, scapula; st, sternum; c, coracoid ; f, furcula ; A, humerus; 

 c.v, cervical vertebrae ; tr, trachea: S.B, secondary remiges. 

 2. The same part, left side, of Gallinula chloropus. B, slip, biceps slip; 

 t.p.l, tensor patagii longus. 



Plate XV. 

 Fig. 1. Muscles of right side of interior of pelvis and inner side of thigh of 

 Chauna derbiana, the muscles of the anterior abdominal wall having 

 been removed. o.i, obturator intern us ; Amb, Ambiens; Quad, 

 Quadriceps extensor ; Ad, adductor ; s.t, semitendinosus. 

 2. The same parts of Euplocamus albocristatus, similarly lettered, sart, 

 sartorius. 



4. Notes on Entozoa. Part III. By T. Spencer Cobijold, 

 M.D., F.R.S., F.L.S., Correspondent of the Academy of 

 Sciences of Philadelphia. 



[Received January 18, 1876.] 



(Plate XVI.) 



In continuing the "Notes" commenced in \H7^, I may observe 

 that I have recently received important additions from naturalists 



