b. The male, distinguished by a greater development of the hind-limbs and a prehensile tail, clasps the female in the lumbar and caudal regions: The Euproctus-group of newts: Triton asper, T. rusconii, and T. montanus.
The act of fecundation of most of the other kinds of Urodela, notably Cryptobranchus, Amphiuma, Proteus, has not yet been observed.
Embracing of the two sexes is the universal rule with the Anura, the male creeping on to the back of the female and clasping her firmly with the arms and hands either in the inguinal region, higher up, or under the armpits. See the numerous statements in the systematic part. This often extremely forcible, pressing embrace seems to be necessary, although the females can deposit the eggs without the help of the male, but in such cases the expulsion takes place at irregular intervals instead of at one time. When the eggs appear at last, and this happens in many species many hours, or even some days, after the beginning of the embrace, the male voids the contents of its seminal vesicles over them. Fertilisation is consequently external, with the possible exception of Pipa, q.v. p. [152].
Deposition of the eggs and nursing habits.–The majority of the Amphibia are oviparous, but some Apoda and Urodela are viviparous. It is unnecessary to call the latter condition ovo-viviparous, since this is really a distinction without a difference.
Viviparous forms:–amongst Urodela; Salamandra maculosa, the young burst the egg-membrane in the act of being born, and are provided with long gills; S. atra, the young undergo their whole development and metamorphosis within the uterus (see p. [119]); Spelerpes fuscus, the young are likewise born in the perfect condition: amongst Apoda; Typhlonectes compressicauda and Dermophis thomensis.
The oviparous Apoda, at least Ichthyophis and Hypogeophis, and a few of the Urodela, as Desmognathus and Amphiuma, take care of their eggs by coiling themselves around them in a hole underground.
Nursing habits are very common amongst the Anura. Boulenger[[28]] has summarised the various conditions concerning the deposition and care that is taken of the eggs, in the following list, in which more recent discoveries have been interpolated.
I. The ovum is small, and the larva leaves it in a comparatively early embryonic condition.
A. The eggs are laid in the water:–
a. Without further care or preparations: probably the majority of Anura; all European forms, except Alytes.