SECRETOEY SACS IN TELEOSTEI. 5o5 



Tunny, viviparity occurs in Zoarces and in other Teleosts ; and 

 iu Anahleps it is said that " the vascular yolk-sac is provided 

 with villi vphich absorb nutriment " from the fluid secreted by 

 the walls of the dilated ovary within which the embryo develops *. 

 The Elasmobrauchs offer numerous instances of this kind ; and 

 Professor Howes (who has aided me liberally with the literature 

 throughout my work) has at the last moment drawn my attention 

 to another case which compares in its " uniqueness " with the 

 divergent specimen of Gynoglossus. In the Anurous Amphibia 

 he has shown f that the epiglottis — an accessory voice-orgau 

 peculiar to Mammals— is of frequent occurrence in an elementary 

 form, liable to great individual variation. In CMroleptes australis 

 the epiglottis was developed iu one specimen, a male; in another, 

 also a male, it was insignificant ; whilst in a third, a female, the 

 epiglottis was small and the accompanying " epilaryngeal folds " 

 absent. He informs me that three more adults, which he has 

 examined since his paper was vn-itten, were wholly destitute of 

 the organs in question. So far, therefore, only one specimen of 

 this species has been found with these organs well-developed. 

 "With the exception perhaps of this last case, the foregoing are all 

 examples of separate specializations in the respective modes of 

 life of the animals, and show once more how plastic is the 

 organism in the grasp of its environment. 



EXPLANATION OF PLATE 38. 



Fig. L Semidiagrammatic transverse section across the nasal region of a 

 Pleuronectid (Plaice or Halibut), to show the nasal secretory sacs, 



The Dipnoi occupy the second stage, where a rudimentary true palate is repre- 

 sented by the hinder portion of the upper lip anterior to the teeth, but where 

 no true maxillae are developed. The palate (?) is here formed by the nasal 

 processes (c/. Semon, I. c), and the naso-pharyngeal communications arise from 

 the primary nasal grooves. The Amniota show the third and last stage. The 

 palate and the internal nares are formed as above, and the maxilla grow round 

 anteriorly to complete the external boundaries of the mouth. 



* Haddon, A. C. : 'The Study of Embryology,' p. 98. {Cf. Wyman— 

 Boston Journ. Nat. Hist. vol. vi. p. 432.) My best thanks are due to Mr. A. 

 W. Kappel, the resourceful Librarian of the Linnean Society, for the pains 

 with which he has determined this reference. 



t Howes, G. B. : " On an unrecognized feature in the Larynx of the 

 Anurous Amphibia." Proc. Zool, Soc. 1887, p, 497. 



