1888.] THE CARPUS AND TARSUS OF THE ANURA. 143 



aid and advice always most cheerfully given ; while we have to 

 tender thanks to Prof. W. K. Parker for useful specimens, to Prof. 

 Wiedersheim of Freiburg for the limbs and a larva of Pipa, to Prof. 

 W. N. Parker for some exquisitely preserved tadpoles of the 

 Common Frog, and to Dr. G. Baur, of New Haven, Conn., for 

 suggestions and advice. 



Some of our best results have been obtained from feet in which 

 ossification was just commencing (ex. fig. 5). At this stage the 

 outlines of the cartilages are more clearly defined than at the earlier 

 ones {cf. fig. S), while there is a total absence of any distortion or 

 displacement consequent upon complete ossification (cf. figs. .5 & G). 

 Identification of this stage by external appearances is very difficult ; 

 absolute size, moreover, gives no clue to it, for while in a Xenophrys 

 measuring 27 millim. from mouth to vent (fig. 14) all expectations 

 were realized, in a Brachycephalus of 20 millim. ossification was 

 found to be complete. 



d. Methods. — We early discarded the section-cutting method 

 employed by Born (3, 6), chiefly because the results finally arrived 

 at were less satisfactory than those obtainable from clarified prepara- 

 tions. Clarification in potash solution (kindly suggested to us by 

 Prof. Wiedersheim) was tried, but relinquished, chiefly on account 

 of the diflSculties experienced in mounting the preparations. Better 

 results were arrived at by clarifying in a mixture of glycerine and 

 potash, and mounting permanently in glycerine jelly ; but our best 

 results were all obtained by the use of clove oil, which offers 

 additional advantages in allowing the preparations to be stained. 

 Borax-carmine solution proved most serviceable as a dye ; less 

 successful preparations were, however, obtained with picro-carmine, 

 hsematoxylin, and bismarck-brown. 



Our method of procedure was generally as follows : — The limb 

 having been carefully skinned, the larger muscles were dissected off", 

 in order to facilitate staining. The preparation was next immersed 

 for about ten minutes in borax-carmine, and then transferred to 

 acid alcohol (75 parts alcohol, 3 parts HNO3, and 22 parts water), 

 in order that sujjerfluous stain might be removed ; after dehydration 

 in absolute alcohol, it was allowed to remain in oil of cloves. The 

 final process consisted in carefully picking away the soft parts, little 

 by little, with two pairs of small forceps under a simple microscope, 

 while the preparation was still immersed in a glass trough of clove 

 oil. The smaller preparations were ultimately mounted in Canada 

 balsam. 



The above method admits of an examination of all parts iu the 

 undisturbed state, and consequently of an accurate determination of 

 the relationships of apposed surfaces, such as is not possible with any 

 other. Moreover, in that ossific centres, lines of fusion, furrows, or 

 outstanding processes are rendered equally obvious, it is manifestly 

 not open to objections which might conceivably arise out of exclusive 

 rehance upon the section-cutter's art. 



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