No. 1. — Studies on Lepidosteus. Part I. By E. L. Mark. 1 



Contents. 



I. 



II. 

 III. 



IV. 



Introduction 1 



Habits of the Young Fishes . 5 

 The Respiratory Function of 

 the Air-Bladder 13 



Embryology ... ... 



1. Egg Membranes .... 



A. Observations .... 



a. Zona Radiata and Vil- 

 lous Layer .... 



6. Micropyle .... 



c. Granulosa .... 



d. Origin of the Zona Ra- 



diata and the Villous 

 Layer 



27 

 27 

 23 



28 

 43 

 45 



48 



Summary 115 



Postscript 119 



Page 



B. Historical and Critical Review of 

 the Literature on the Primary 

 Egg Membranes and the Mi- 

 cropyle in Fishes 54 



a. Cyclostomata .... 54 



b. Selachii 60 



c. Ganoidei 63 



d. Dipnoi 66 



<?. Teleostei 67 



1. Zona Radiata and Vil- 



lous Layer .... 68 



2. Capsular Membrane . 94 



3. Micropyle and Plug . 102 



4. Micropylar Cell . . . 110 



Bibliography 120 



Explanation of Figures 128 



I. Introduction. 



I became deeply interested in the embryology of Lepidosteus through 

 reading the paper on that subject published by Mr. Agassiz in 1878, and 

 determined to avail myself of the first opportunity of following up the 

 study. I desired particularly to pursue the development of the early 

 stages. A little later I was further incited to this by the brief account 

 of it which Balfour gave iu the second volume of his Comparative Em- 

 bryology (1881). 



I had already formed plans for going to Black Lake, in the vicinity 

 of Ogdensburg, N. Y., in the spring of 1882, for the purpose of getting 

 material for the contemplated study, when I learned from Mr. Agassiz 

 that Balfour had in hand an extensive paper on the subject. Mr. Agas- 

 siz also informed me that he still had left a part of the material from 

 which Balfour had been supplied, and he kindly placed this at my 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology at Harvard College, No. XV. 



VOL XIX. — NO. 1. 1 



