1880.] Structure and Development of Skull in the Batracliia. 435 



is because the true conduction current is so much greater propor- 

 tionally in water than in glass. In certain experiments, which we 

 hope to have the honour of describing fully in a future paper, we have 

 been able to make an approximation to the time integral of this con- 

 duction current during the small times of first charge and discharge, 

 and by subtracting it from the measured charge, or adding it to the 

 measured discbarge, we have obtained what we may reasonably call 

 the true induction charge in a voltameter. We mention this now since, 

 although years ago Mr. Cromwell Varley referred to the electrostatic 

 capacity of voltameters, the investigation of this instantaneous charge 

 has been neglected, because this charge is small compared with the 

 residual one, just as the important investigation of the residual 

 charge in Leyden jars was for a long time not carried out, because 

 the residual charge was small compared with the instantaneous 

 charge. 



For assistance rendered in the carrying out of the series of experi- 

 ments, the results of a few only of which are given in this preliminary 

 account, we have to thank the following of our students: — Messrs. 

 Fujioka, Igarashi, Iida, Inoguchi, Kasai, Kawaguchi, Mita, Nobechi, 

 Oshima. 



III. " On the Structure and Development of the Skull in the 

 Batrachia. Part III." By W. K. Parker, F.R.S. Received 

 April 29, 1880. 



(Abstract.) 



Some of the work brought forward in this paper was in hand before 

 the first part was in print. That initial piece of work dealt only with 

 the formation of the skull in the common frog, but it was followed by 

 another which appeared in the " Philosophical Transactions " in 1876, 

 which treated of the skulls of the common and of the " aglossal " toads. 



Of the latter types only two kinds are known, viz., the nailed toad 

 of the Cape (Dachjlethra) , and the monstrous toad of Surinam (Pipa). 

 All the bulk of the Batrachia are included in the sub-group " Opis- 

 thoglossa," these have a tongue, and in most cases it is free behind and 

 not in front ; the " Proteroglossal " Batrachia are very few in number, 

 and the character itself (as Dr. Gtinther informs me) is not well 

 pronounced. 



I have now worked out the skull, in one or more stages, in about a 

 tithe of the known species, and in my second paper in both of the 

 aberrant (" aglossal ") types ; in them this was done in various stages. 



I am not aware that there is any " order " of any " class " in the 

 Yertebrata where so large a percentage of species has been, or indeed, 



