504 H. H. SWINNERTON. 



knowledge of the development of the Teleostean head skele- 

 ton ; McMurricli (83) is the only investigator who has dealt 

 with the development of the whole head skeleton of any other 

 type with any approach to detail; Pouchet (78) has dealt 

 with isolated stages of Gobius, Synguathus, Labrus, Atherina, 

 and Engraulisj Stohr (83) has confined himself to extending 

 or rectifying Parker's observations ; whilst Ganin (80) has 

 devoted two pages to these processes in the skull of Gaster- 

 osteus and Rhodeus. Several others have dealt with the 

 development of parts with more or less detail. 



It was with a view towards supplying this deficiency that 

 the investigation, the results of which are here recorded, was 

 undertaken. Acting upon a suggestion originally made by 

 Professor G. B. Howes, the common three-spined stickleback 

 was chosen as the basis of my observations, partly because 

 of the ease with which the material could be obtained, and 

 since, while it offered a more specialised type than the 

 salmon, it seemed to form, according to Cope (70) and later 

 systematists, a suitable starting-point for the study of certain 

 specialised and peculiar groups, e.g. Lophobranchs. 



Beyond the work of Ganin the only previous observa- 

 tions upon the skull of Gasterosteus which 1 have been 

 able to find are those of Huxley (58 and 59), chiefly in his 

 Croonian Lecture " On the Theory of the Vertebrate Skull." 

 Figuring and describing the hyosuspensorial apparatus of 

 the adult, he gives three figures of the larval skull, which are 

 remarkable for their accuracy. One figure represents a 

 stage coincident with my Stage II, and the other two 

 correspond to my Stage IV. Amongst his original drawings, 

 now preserved in the Huxley laboratory, are several other 

 figures of the same stages, which were evidently studies for 

 parts of those which he published. 



I tender my heartiest thanks to Professor G. B. Howes for 

 his ever-ready help in obtaining material, his guidance in 

 working, with the reading, and also to Mr. M. F. Woodward 

 and Mr. G. A. Bouleuger for much valuable assistance. 



