192 PRINCIPLES OF ANIMAL BIOLOGY 



elaborate copulatory process and capsule-formation, as diescribed in 

 the preceding chapter. 



Fertilization in Dioecious Species. — In many aquatic animals the 

 sexual elements or at least the spermatozoa are simply discharged into 

 the water and the germ cells come together by chance. Thus in the 

 jelly fishes the spermatozoa are liberated into the water, and may happen 

 to meet the eggs, which are retained in the ovary of the female; in the 

 starfishes and sea-urchins both eggs and spermatozoa are poured into 

 the water, where they may or may not chance to come in contact. In 

 other animals there is congregation of the sexes at the breeding time and 

 the eggs and sperms are liberated in proximity. This congregation 

 makes it more likely that the germ cells will meet, but chance still plays 



.,-: an important role. The giant salamander 



%;s. >^l Cryptobranchus is a form that congregates 



with its fellows at the breeding season. In 

 certain other salamanders, those of the 

 genus Ambystoma, the male deposits the 

 spermatozoa in a naked, nearly spherical 

 mass resting on a gelatinous stalk which is 

 attached to a leaf or some other object in 

 the water. This structure, including the 

 Fig. 146.— Spermatophore of gtalk, is called a sverniatovhore (Fig. 146). 



Notophthalmus viridescens mndescens rm p • • i 



(Raf.), the common newt of eastern The masS of spermatOZOa at its top IS sub- 



North America. The stalk is a gequently nipped off by the female with 



clear gelatinous substance; the , ,. r i i ^ .^ 



apical mass (dotted in the figure) the lips ot the cloaca, and the eggs are 

 is a snowy-white mass of seminal fertilized within her body. There is no 



fluid containing spermatozoa. The . 



mass of spermatozoa is taken up copulation nor amplexus among any of the 

 by the cloaca of the female. (After forms just mentioned. Copulatory habits 

 B. G. Smith.) j_ i p i i 



are to be found, however, among some 

 forms in which fertilization does not take place until after the eggs are laid, 

 as well as among those in which the eggs are fertilized within the body of 

 the mother. Furthermore, the eggs may or may not be fertilized at the 

 time of copulation or amplexus. In the tailless amphibians (the frogs 

 and toads) and some fishes the sexes congregate during the breeding sea- 

 son, the male clasps the female, and the seminal fluid is poured over the 

 eggs as they are emitted (Fig. 147). Here the fertilization occurs during 

 or just after amplexus. In the crayfishes, however, the spermatozoa 

 transferred during copulation are stored in a seminal receptacle in the 

 abdomen of the female, from which they are presumably emitted to fer- 

 tilize the eggs as these are laid several months later. In some of the 

 salamanders in which the male deposits spcrmatophores amplexus also 

 occurs. In this respect these species differ from Ambystoma, mentioned 

 above, in which there is no amplexus. Thus, in Notophthalmus viridescens 

 the males clasp the females and deposit the spermatophores afterwards, 



