The shape and size of the egg mass is characteristic of the species

Frogs' embryos are typically surrounded by several layers of gelatinous material. When several eggs are clumped together, they are collectively known as frogspawn. The jelly provides support and protection while allowing the passage of oxygen, carbon dioxide and ammonia. It absorbs moisture and swells on contact with water. After fertilization, the innermost portion liquifies to allow free movement of the developing embryo. In certain species, such as the Northern red-legged frog (Rana aurora) and the wood frog (Rana sylvatica), symbiotic unicellular green algae are present in the gelatinous material. It is thought that these may benefit the developing larvae by providing them with extra oxygen through photosynthesis.[108] Most eggs are black or dark brown and this has the advantage of absorbing warmth from the sun which the insulating capsule retains. The interior of globular egg clusters of the wood frog (Rana sylvatica) has been found to be up to 6°C (11°F) warmer than the surrounding water and this speeds up the development of the larvae.[109]

The shape and size of the egg mass is characteristic of the species. Ranids tend to produce globular clusters containing large numbers of eggs whereas bufonids produce long, cylindrical strings. The tiny yellow-striped pygmy eleuth (Eleutherodactylus limbatus) lays eggs singly, burying them in moist soil.[110] The smoky jungle frog (Leptodactylus pentadactylus) makes a nest of foam in a hollow. The eggs hatch when the nest is flooded, or the tadpoles may complete their development in the foam if flooding does not occur.[111] The red-eyed treefrog (Agalychnis callidryas) deposits its eggs on a leaf above a pool and when they hatch, the larvae fall into the water below.[112] The larvae developing in the eggs can detect vibrations caused by nearby predatory wasps or snakes, and will hatch early to avoid being eaten.[113] In general, the length of the egg stage depends on the species and the environmental conditions. Aquatic eggs normally hatch within one week when the capsule splits as a result of enzymes released by the developing larvae