EGGS 



CHAPTER 16 



Most of us no longer trouble ourselves over the old problem as to which 

 came first, the hen or the egg, but in our trips afield we may frequently won' 

 der just what animals are likely to hatch from the eggs we may find, since not 

 only the hen but all birds, turtles, many snakes, lizards, salamanders, frogs, 

 fish and many invertebrates lay fairly conspicuous eggs. The first indications 

 as to the possibilities of a strange egg are the habitat in which it occurs and the 

 nature of its outer covering. Size, shape, color and deposition singly or in 

 bunches all furnish additional clues. 



Eggs laid in water are almost invariably covered with a gelatinous coat 

 or coats, which serve as protection against hungry animals and as a means of 

 concentrating heat to speed up development. By means of this greenhouse 

 construction it is possible for eggs to develop, even though the pond be full 

 of floating ice. The eggs most likely to attract attention are those of fish and 

 amphibians. Other eggs commonly found in water are those of arthropods, es- 

 pecially insects, and of mollusks. The invertebrate eggs are usually individually 

 smaller than those of water vertebrates, although the egg masses may be quite 

 conspicuous. 



Fish eggs are found in groups of many separate eggs, or in bunches or 

 masses. In general fish eggs may be recognized by a uniformly milky or irides' 

 cent appearance without conspicuous, supplementary, jelly envelopes, so that 

 they resemble a mass of boiled tapioca. Some fishes lay colored eggs, those of 

 the carp, for example, being red and those of the sturgeon being various shades 

 of brown. Fish eggs are often deposited in a nest or circular depression in the 

 pond or stream floor or in a hollow in the bank or under a sunken log. Usually 

 the male parent is close by to guard the nest. Many trout bury many separate 

 eggs in gravel or under small stones. The perch and pickerel lay in shallow 

 water among twigs or water weeds and deposit strings of many eggs in close 

 2;igzag or spiral arrangement. A few fishes, such as the sticklebacks, build 

 elaborate nests, much like those of birds, among the water weeds. 



Salamander eggs are laid either singly or in masses. Most of the Amhy' 

 stomidae lay bunches of dark-colored eggs with one or more envelopes around 

 each indivdual egg and with a common jelly envelope around the Vv'hole mass. 

 They may be distinguished from frog eggs by means of this common envelope, 

 which is not characteristic of the latter. Most of the Ambystoma group lay 

 in early spring, many of them while the ponds are still full of floating ice, 

 attaching the egg masses to sticks and water plants a few inches below the 



536 



