SOME ORGANS AND VESTIGES OF ORGANS, WHICH 

 SHOW [STRUCTURAL COMMUNITY WITH] VERY 

 PRIMITIVE VERTEBRATE TYPES 



CONDITIONS DEFINITIVE IN FISHES (ELASMOBRANCHS) AEE 

 INDICATED BY 



(1) The free dental papillae projecting above the surface of 

 the mucous membrane before the sinking of the dental ridge. 



(The appearance ontogenetically of the dental ridges, long- 

 before the first osseous rudiments, points back to the 

 extremely early phylogenetic appearance of teeth, in 

 Vertebrates, before any of the other hard structures of 

 the body.) 



(2) The pineal gland and pineal organ (a parietal foramen 

 in the roof of the skull is found in Fishes as early as the 

 Devonian period, and the organ occurs in the Marsipobranchii). 



(3) The pituitary body (hypophysis cerebri). 



(4) The branchial pouches. 



(5) The vessels of the visceral arch system. 



vj (6) The vasa hyaloidea of the vitreous body (Cloquet's 

 canal). 



(7) The cardinal veins. 



(8) Certain structures, appearing in the development of the 

 heart, vestiges of which are found in the fully developed organ. 



(9) The arteria caudalis (A sacralis media). 



(10) The pro- and naeso-nephric excretory apparatus. 



(11) The possible vestiges of a third set of teeth (pointing 

 back to a probable successive renewal of teeth, such as 

 characterises Fishes, Amphibians, and Reptiles). 



