ON THE DEVELOPMENT OF PARASITIC COPEPODS. 75 



tion (epibole). It is probable that all the mesoderm arises from 

 cells turned under the lip of the blastopore. 



2. The entrance of supernumerary spermatozoa into the egg 

 so greatly disturbs the process of development that the latter is 

 either prevented or so distorted that it never progresses very far, 

 and then in an abnormal manner. 



3. The compressed condition of the egg affects the cleavage : 

 (i) by altering the arrangement of the protoplasmic cells, (2) by 

 necessitating increased length of the spindles in the yolk cells, 

 (3) by preventing cleavage of the yolk, and (4) by increasing the 

 surface of the egg and retarding gastrulation (epibole). But it is 

 very improbable that slight alterations in the amount and direc- 

 tion of compression have as great an influence on development 

 as supposed by Schimkewitz. I found nauplii which were appar- 

 ently normal (save perhaps in size) hatching from hemispherical 

 eggs. As the nauplius hatches it immediately rounds up, and 

 assumes the same form whether it arise from a hemispherical or 



from a very flat egg. 





 VIII. EXPLANATION OF PLATES. 



ABBREVIATIONS. 



an ' = First antenna. 



an 2 = Second antenna. 



b - Blastopore. 



e - Entoblast cell. 



en - Entoblast nucleus. 



ec = Ectoderm cell. 



f = Deeply staining protoplasm. 



g = Germ cell. 



m = Muscle cell. 



M 2 = Mesoblast of first antenna. 



>n z - Mesoblast of second antenna. 



m* = Mesoblast of mandible. 



w s-io _ Mesoblast of post nauplius appendages. 



md Mandible. 



nip - Postnauplius rnesoblast. 



' = Procerebrum. 



n 2 Neuromere of first antenna. 



n 3 - Neuromere of second antenna. 



w 4 = Neuromere of mandible. 



n 5 ~ 10 = Neuromeres of post nauplius segments. 



o = Rudiment of mouth. 



0' = Rudiment of lateral eye. 



om = Rudiment of median eye. 



x - Darkly staining cell in yolk. 



