THE DEVELOPMENT OF THE HYBEIDS BETWEEN FUNDU- 

 LUS HETEEOCLITUS AND MENIDIA NOTATA WITH 

 ESPECIAL EEFEEENCE TO THE BEHAA^OE OF THE 

 MATEENAL AND PATEENAL CHEOMATIN. 



BY 



WILLIAM J. MOENKHAUS, Ph. D. 

 With 4 Plates. 



contents. 



page pace 



I. Introduction 29 4. General Review of Literature 41 



II. Material and Methods 30 5. Conjugation of Pronuclei and the 



III. Nomenclature 31 First Cleavage 43 



1\ . Fertilization 32 6. Second Cleavage 44 



V. Development 33 7. The Rotation of Nuclei 46 



1. Cleavage 33 8. Third Cleavage 47 



a. Form of Cleavage 33 9. Fourth Cleavage 48 



b. Rhythm of Cleavage 35 10. Later Cleavage *8 



2. Development of Dispermic Eggs. 36 11. Comparison With Other Forms. . 50 



3. Later Development 37 12. Maternal and Paternal Nucleoli. 52 



VI. The Individuality of the Maternal 13. The Persistence of the Individual 



and Paternal Chromosomes 39 Chromosome 53 



1. Introduction 39 Summary 54 



2. Material and. Methods 39 Papers Cited -.-.... 56 



3. Description of the Chromosomes. 40 Explanation of Plates 58-64 



• I. Inteoduction. 



During the summer of 1899, while endeavoring to find two species 

 of fishes that I could readil}^ hybridize with the view of making certain 

 variation studies on hybrids, I began what has since grown into a rather 

 extensive series of experiments on the limits of crossing in fishes. Among 

 many crosses effected, the one which proved of special interest both then 

 and since, is that between Fnndulus heteroclitus and Menidia notata. 

 The results of the other crosses I have reserved for another paper. In 

 the following pages only the results obtained on the above-named hybrid 

 are considered. 



In addition to their availability, the long period over which they 

 spawn and the ease with which they can be hybridized, the reason for 

 making a special study of the hybrids between Fundulus heteroclitus 

 and Menidia notata, is the fact that the cliromosomes of the two species 

 can be readily distinguished morphologically. This fact is a distinct 

 advantage in following out the nuclear history with reference to the im- 



Ameeican Journal op Anatomy. — Vol. III. 



