326 ON THE ANATOMY OF 



which was afterwards remarkably confirmed by Garrod's observations on 

 their myology and visceral anatomy. 



The fact that there should be important cranial differences between 

 the two groups (and even amongst the members of one of these) only 

 shows that the cranial structure of a bird may be profoundly changed, 

 in accordance with its conditions of existence, whilst in the rest of 

 its organs no change whatever is effected ; and such a fact must of 

 itself tell heavily against the view that the structure of the skull in 

 birds is of itself alone a certain, or even sufficient, index to their sys- 

 tematic classification. 



P * Z 208 1882 ' 56 ' ON SOME POINTS IN THE ANATOMY OF THE 

 INDIAN DARTER (PLOTUS MELANOGASTER), AND 

 ON THE MECHANISM OF THE NECK IN THE 

 DARTERS (PLOTUS), IN CONNEXION WITH THEIR 

 HABITS.* 



IT is to the late Prof. Garrod that we are indebted for our knowledge 

 of the great differences in the anatomy of the digestive organs of the 

 Americant (Plotus anhinga) and African J (P. levaillanti) Darters. 

 The existence of such differences in birds apparently so nearly allied 

 made it very desirable to obtain a knowledge of these parts in the other 

 species of the genus Plotus. 



On April 8th last, the Society obtained, by exchange from the 

 Zoological Gardens of Calcutta, the first specimen of the Indian Darter 

 P. Z S. 1882, (Plotus melanogaster) that it has acquired. The specimen, a male, lived 

 p. 209. in excellent health till December 21st last, when it died suddenly, its 

 death apparently having been caused by some sudden shock produced 

 by too rapid feeding, as a dozen small fishes, just swallowed, were found 

 in its stomach. No disease whatever could be found. It is this speci- 

 men that forms the subject of the present communication. 



As regards its stomach, Plotus melanogaster closely approaches P. 

 levaillanti, the proventriculus being in the form of two quite separate 

 patches, and the pyloric lobe being provided with a similar hair-covered 

 conical and retractile " plug." In P. anhinga, it will be remembered, 

 the proventricular glands are collected together into a special diverti- 

 culum of the stomach, whilst the pyloric lobe, though hairy internally, 



* Proc. Zool. Soc. 1882, pp. 208-212. Eead Feb. 7, 1882. 



t P. Z. S. 1876, pp. 335-345 ; Scient. Papers, pp. 334-346, pis. xviii.-xx. 



| L. c. 1878, pp. 679-681 ; t. c. pp. 346-349. 



