Vol. XII. January, /po/. No. 2. 



BIOLOGICAL BULLETIN 



ON THE DEVELOPMENT OF PARASITIC COPEPODS. 1 



PART II. 



J. F. McCLENDON. 



CONTENTS. 



I. Cleavage of the egg 57 



1 . Lcemargiis muricatus 57 



A. First cleavage 57 



B. Second cleavage 5& 



2. The Dichelestid 60 



A. First cleavage 60 



B. Second cleavage 60 



C. Third cleavage 60 



D. Fourth cleavage 60 



E. Fifth cleavage 61 



F. Sixth cleavage 61 



II. On the nature of the cleavage process 62 



III. The mesoblast 63 



1. The nauplius mesoblast 63 



A. The germ cells 63 



a. Pandarus sinnatus 63 



b. The dichelestid 65 



B. Mesoblastic rudiments of the nauplius appendages 65 



2. Post-nauplius mesoblast 67 



IV. The entoblast 68 



V. Polyspermy 69 



VI. Relation of pressure, polyspermy, etc., to the type of cleavage 7 



VII. Summary 74 



VIII. Explanation of plates 75 



IX. Bibliography 76 



The egg is covered by a chitinous chorion and the eggs are 

 packed (and much compressed) in a tough chitinous tube (e. c., 

 Text Fig. i), which is attached to the mother. In order to allow 



1 Thesis accepted by the Faculty of the Department of Philosophy of the Univer- 

 sity of Pennsylvania toward the degree of doctor of philosophy. 



53 



