{PERENNIBRANCHIATA {Trachystomata. { {Proteidæ. II. Urodela. {CADUCIBRANCHIATA {Amphiumidæ. { {Menopomidæ. {MYCTODERA {Amblystomidæ. {Salamandridæ. III. Gymnophiona. The eggs of most Amphibia[43] are laid in water. They are smallish nearly spherical bodies, and in the majority of known Anura (all the European species), and in many Urodela (Amblystoma, Axolotl, though not in the common Newt) part of the surface is dark or black, owing to the presence of a superficial layer of pigment, while the remainder is unpigmented. The pigmented part is at the upper pole of the egg, and contains the germinal vesicle till the time of its atrophy; and the yolk-granules in it are smaller than those in the unpigmented part. The ovum is closely surrounded by a vitelline membrane[44], and receives, in its passage down the oviduct, a gelatinous investment of varying structure. [43] I am under great obligations to Mr Parker for having kindly supplied me, in answer to my questions, with a large amount of valuable information on the development of the Amphibia. [44] Within the vitelline membrane there appears to be present, in the Anura at any rate, a very delicate membrane closely applied to the yolk. In the Anura the eggs are fertilized as they leave the oviduct. In some of the Urodela the mode of fertilization is still imperfectly understood. In Salamanders and probably Newts it is internal[45]; but in Amblystoma punctatum (Clark, No. 98), the male deposits the semen in the water. The eggs are laid by the Anura in masses or strings. By Newts they are deposited singly in the angle of a bent blade of grass or leaf of a water-plant, and by Amblystoma punctatum in masses containing from four eggs to two hundred. Salamandra atra and Salamandra maculosa are viviparous. The period of gestation for the latter species lasts a whole year. [45] Allen Thomson informs me that he has watched the process of fertilization in the Newt, and that the male deposits the semen in the water close to the female. From the water it seems to enter the female generative aperture. Von Siebold has shewn that there is present in female Newts and Salamanders a spermatic bursa. In this bursa the spermatozoa long (three months) retain their vitality in some Salamanders. Various peculiarities in the gestation are to be explained by this fact. A good many exceptions to the above general statements have been recorded[46]. [46] For a summary of these and the literature of the subject _vide_ "Amphibia," by C. K. Hoffmann, in Bronn's _Classen und Ordnungen d. Thier-reichs_.