328 Miss Johnson, On the development of the Pelvic Girdle [Feb. 26, 



present condition of a closed central canal, whose function it is not 

 within my province to examine. 



Before concluding I wish to point out that a canal leading into 

 the centre of the central nervous system, is not confined to the 

 vertebrata. Such canals are present leading into the cephalic 

 ganglia of adult Nemertines, and in the most conspicuous part of 

 the nervous system of Balanoglossus, a similar arrangement of a 

 very complicated nature exists 1 . They are also present in the 

 cephalic ganglia of the embryos of most tracheate animals. 



The cephalic pits in the tracheata served, according to my 

 view, for respiration in the aquatic ancestors of the living forms. 

 The development of tracheae is not at present known, but I think, 

 that if there is any truth in the hypothesis of the original function 

 of these tracheate cephalic pits, it will be found that the trachea 

 of the cerebral ganglia arise from the epiblastic cells lining 

 these pits. 



(2) On a new microtome, designed to increase the accuracy and 

 rapidity of section cutting. By W. H. Caldwell, B.A. 



(3) On the development of the Pelvic Girdle and Skeleton of the 

 Hind Limb in the Chick. By Alice Johnson, Newnham College. 



The following paper contains a summary of the conclusions 

 arrived at by a study of the development of the pelvic girdle and 

 hind limb of the Chick. The investigation was undertaken at the 

 suggestion of the late Prof. Balfour, with the view of testing the 

 comparison which Marsh had instituted between the pelvis of 

 Dinosaurs and that of Birds. I hope to publish later a full 

 account — with figures — of my results. 



In the Chick, as in the Elasmobranch, the skeleton of the hind 

 limb is developed continuously with the pelvic girdle, the parts of 

 the girdle which are nearest to the skeleton of the limb are first 

 developed, and the dorsal and ventral elements appear later, so 

 that the girdle may be said to be an outgrowth from the femur. 



The chief points which will be considered here are the relations 

 of the pubis in the embryo, and the conclusions which may be 

 drawn from thence as to the homologies of the pubis in Birds with 

 that in other types. r „ 



Both the pubis and ischium, as Bunge 2 has described, are at 

 first placed with their long axes at right angles to the long axis of 

 the ilium, and afterwards rotated backwards, so as to occupy the 

 position in which they are found in adult Birds, where the long 

 axes of all three bones are parallel to one another. Bunge and 

 other writers following him have asserted that the pubi% is at first 



1 From an unpublished research by Mr W. Bateson, of St John's College. 



2 A. Bunge, " Untersuchungen zur Entwickelungsgeschichte des Beckengiirtels 

 der Amphibien, Beptilien und Vogel." Dorpat 1880. 



