Vol. XIV. May, ipo8. No. 6. 



BIOLOGICAL BULLETIN 



AN INTRA-NUCLEAR MITOTIC FIGURE IN THE 



PRIMARY OOCYTE OF A COPEPOD, CAN- 



THOCAMPTUS STAPHILINUS JUR. 



ROBERT W. HEGNER. 



The oogenesis and early development of the eggs of free liv- 

 ing copepods has been studied by several investigators princi- 

 pally Hacker and Riickert. The former ('92, '95) has described 

 the maturation processes in Cyclops, Canthocamptus and several 

 other species. Riickert ('94) studied the polar-body formation 

 in Cyclops, Heterocope and Diaptonuis. The development of the 

 eggs of parasitic copepods has also received the attention of em- 

 bryologists (McClendon, '06). 



As far as I have been able to learn none of these investigators 

 has reported the presence of polar rays in the mitotic figure of 

 the first maturation division. Riickert ('94) maintains that the 

 centrosomes of the first maturation spindle {Cyclops) have an 

 intra-nuclear origin ; they pass to either end of the nucleus, but 

 no polar rays were reported. Hacker ('95) in Canthocamptus 

 staphylinus figures a spindle with chromosomes arranged in an 

 equatorial plate lying entirely within the nuclear membrane of an 

 oogonium which is undergoing its last division. Here also no 

 astral fibers are evident. Parasitic copepods apparently do not 

 depart from this rule for McClendon ('06) tells us that in Pan- 

 davus sinuatus the first maturation figure is " similar to that found 

 in free living copepods having no polar rays." Centrosomes 

 originate within the nucleus in the spermatocytes of Ascaris meg- 

 alocephala, var. univalens (Brauer, '93) but wander outside of the 

 membrane before the astral fibers appear. This is apparently the 

 order of events in the half-dozen other cases where an intra- 

 nuclear origin of the centrosomes has been asserted. 



While collecting Hydra with Mr. C. T. Vorhies during the month 



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