MAY 8 1900 



No. 8. — Maturation and Fertilization in Pulmonate Gasteropods. 1 



By Henry E. Linville. 



CONTENTS. 



Introduction 213 



Collection of Material .... 214 

 Technique 215 



A. Maturation 217 



I. General Account 217 



1. Limax Eggs in the Oviduct 217 



2. Limax Eggs in the Albumen 



Gland 218 



3. Limax Eggs in the Uterus . 218 



4. Eggs of Limnaea .... 219 

 II. Centrosome and Centrosphere 219 



1. Limax 220 



(a) First Maturation Spindle 220 



(b) Second Maturation Spin- 



dle 222 



2. Limnasa elodes 222 



(a) First Maturation Spindle 222 



(b) Second Maturation Spin- 



dle 226 



III. The Nucleus 228 



1. Division of Chromosomes . 228 



2. Nucleoli, or Karyosomes . 232 

 B. Fertilization 233 



I. The Early History of the Sper- 

 matozoon in the Egg . . . 233 



1. General Description . . . 233 



2. Changes in the Sperm- 



Head 235 



3. The Sperm-Head and the 



Beginning of the Sperm- 



Centrosome 236 



II. The Sperm-Centrosome . . 239 

 III. The Origin of the First Cleav- 

 age Spindle 241 



Summary 244 



Bibliography 246 



Explanation of Plates 248 



INTRODUCTION. 



In the Autumn of 1896 I undertook this investigation at the sugges- 

 tion of my teacher, Professor Mark, to whom I am under mauy obliga- 

 tions for helpful suggestions and criticisms. 



In the beginning my plan was to study the maturation and fertilization 

 of Limax maximus L. and Limax agrestis Muller, but owing to ill fortune 

 and inexperience I was unable to preserve a sufficient amount of 

 properly prepared material of the desired stages, and consequently I 

 have been obliged to supplement my work with the results obtained 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology at Harvard College, under the direction of E. L. Mark, No. 109. 

 vol. xxxv. — no. 8. 



