HYOBRANCHIAL APPARATUS OF SPELERPES 529 



In the carrying out of this plan I shall attempt to give a 

 complete description of the anatomy of the hyobranchial skeleton 

 and of its muscles, without reference to their innervation, in 

 the larva and in the adult, with some reference to the mor- 

 phology of the parts, and shall then try to trace the method of 

 development of the larval apparatus into that of the adult, 

 through the period of metamorphosis. Correlation of the facts 

 found with physiological observations, in the main, fall outside 

 the scope of the present paper. 



2. Material and technique 



I have used a large number of specimens of Spelerpes bislineatus, 

 larval, metamorphic, and adult, many of which had been pre-- 

 viously observed for external physiological phenomena in the 

 living state. I prepared about twenty-five or thirty of these for 

 study of the skeleton by Van Wijhe's methylen-blue method for 

 cartilage. This method was particularly good for the larvae 

 after killing in 10 per cent formalin, but did not give quite such 

 successful results with the adults and metamorphic specimens. 

 Figures 4, 5, 17, 18, and 28 are drawn from such preparations. 



I could dissect the adults very successfully under the binocular 

 microscope, especially if stained first in methylen-blue. Figures 

 19, 20, and 21 are based upon such dissections. For the more 

 detailed work, however; serial sections were the surest method. 

 Several larvae of about 20 to 24 mm. were sectioned for the 

 typical larval condition, and several adults for comparison with 

 my dissections. For the metamorphic phenomena I made series 

 of some eleven specimens, which I afterward found fell into about 

 four distinct stages. My sections are 15 and 20 /x thick and 

 mainly transverse, with a few horizontal and sagittal series for 

 comparison. Delafield's haematoxylin after the picric acid of 

 the decalcifying fluid was the most useful stain. 



Reconstructions were made with millimeter paper (the drawing 

 of the larval muscles (fig. 6) is made from one of these) and 

 certain details I reconstructed with wax plates. But for the 

 main part I relied on rough reconstruction in plastiline, and on 



