THE EMBRYOLOGY OF CRYPTOBRANCHUS ALLE- 



GHENIENSIS, INCLUDING COMPARISONS 



WITH SOME OTHER VERTEBRATES 



I. introduction; the history of the egg before 



CLEAVAGE 



BERTRAM G. SMITH 



Fnnn the Zoological Laboratory of Columbia University 



FIFTY-SIX FIGURES 



CONTENTS 



I. Introduction 62 



II. The adults. 



A. Habitat 66 



B. General characteristics: size, form, coloration 67 



. C. Breeding habits 



1. Breeding season 68 



2. External sexual characteristics 69 



3. Sex ratio and sex segregation 69 



4. The eggs 



(a). General history of the eggs and their envelopes before 



the time of spawning 71 



(b). Oviposition, and nesting habits 73 



(c). The newly-laid egg and its envelopes 74 



o. The spermatozoon 81 



6. The method of fertilization 82 



7. The brooding habit 83 



D. Summary 88 



III. Methods and technique. 



A. The collection and care of living material 89 



B. Fixation and preservation 90 



C. Sectioning and staining 94 



IV. The external history of the egg before cleavage. 



A. External changes preceding and accompanying maturation 96 



B. Capacity of uterine eggs for fertilization 100 



C. Changes visible from the surface during fertilization 101 



D. Summary 106 



61 



