No. 4. Ovogenesis in Distaplia occidentalis ElTTER (MS.), with 



Remarks on Other Species} By Frank W. Banckoft. 



CONTENTS. 



PAGE 



I. Introduction 69 



11. Sexual Organs 62 



1. Development in Distaplia oc- 



cidentalis 62 



Conclusions 66 



2. Structure in the Adult ... 66 

 a. In Distaplia occidentalis . 68 

 6. Observations on Other Spe- 

 cies 73 



c. General Considerations . . 74 



III. Incubatory Pouch 76 



1. Historical Summary ... 76 



2. Observations 77 



IV, Envelopes of the Ovum ... 79 



1. Primitive Follicular Epithe- 



lium 79 



2. Test Cells 80 



a. Evidence for the Intraovu- 



lar Origin of the Test Cells 81 



PAon 



b. Evidence for the Follicular 



Origin of the Test Cells . 82 



c. Degeneration of the Test 



Cells 84 



d. Fate and Function of the 



Test Cells 84 



3. Secondary Follicular Epithe- 



lium 88 



4. Inner Follicular Epithelium . 88 

 6. Outer Follicular Epithelium 



and Corpus Luteum ... 89 

 6. Observations on Styela mon- 



tereyensis 92 



V. Ovum 95 



1. Cytoplasm 95 



2. Germinative Vesicle ... 96 



3. Nucleolus 102 



4. Maturation 105 



Bibliography 109 



Explanation of Plates 112 



I. Introduction. 



The Distaplia material here described was collected by Professor 

 William E. Ritter at Pacific Grove, California, during the summer of 

 1896, and is much of it in an excellent state of preservation. Davi- 

 doff's ('89, p. 118) corrosive-acetic mixture, picro-acetic acid, picro- 

 sulphuric acid, and Perenyi's fluid were used for fixing, and of these the 

 first waa by far the best, and yielded excellent results. 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology at Harvard College, under the direction of E. L. Mark, No. XCVIII. 

 VOL. XXXV. — No. 4. 1 



