MALE GERM (ELLS IN NOTONECTA 97 



protoplasm near the niitocliondrial body. It seems altogether 

 j^i'obable that the centrosome becomes embedded in the mito- 

 chondrial mass at an early stage and remains in connection with 

 it during the growth i:)eriod. It is of interest to note that the 

 orientation of the spireme is not towai'd the nuclear plate but 

 toward the karyosphere; these two bodies may lie in an}^ position 

 relati^'e to each other, the kar3^osphere being usually eccentri- 

 cally placed. 



B. Discussion. 



Mitochondria have been found in many in\'ertebrates and 

 vertebrates in both germ and tissue cells by many observers; 

 Faure-Fremiet ('10). Prenant ('10) and ^Montgomery ('11) have 

 recently gi\'en comprehensive reviews of the subject so that only 

 a few points will be touched on here. Most commonly, mito- 

 chondria appear as fine granules which have a tendency to 

 arrange themselves in rods or chondromites (Meves '00) . In some 

 forms, the mitochondria form long fibers called by Meves ('08) 

 'chondriokonts.' In a few cases the mitochondria have been 

 described as \Tsicles with a dense shell, e.g., by AIe\'es in Pj'gaera 

 COO) and other forms, by Meves and Duesberg ( '08) in the hornet, 

 and by Gerard ('09) in Stenobothrus. In the latter case the mito- 

 chondria occur both in the form of ^'esicles antl fibers and bear a 

 striking resemblance dm'ing the growth period to those of Noto- 

 necta. In Notonecta it is perfectly clear that the fibers are 

 formed not by chains of granules but directly from the vesicles 

 by a disappearance of the surrounding substance; the dense shell 

 described by the above named observers is probably the mito- 

 chondrial fiber in the sphere. Loyez ('09) has found in the egg 

 of tunicates that the mitochondrial fiber develops into a yolk 

 sphere; this is practically the reverse of what occurs in Notonecta. 



In division the mitochondria usually appear to be di\'ided en 

 masse, as they are in Notonecta; but in some of the Pi'otozoa, 

 according to Faure-Fremiet ('10), the individual mitochondria 

 divide at the time of the division of the mici-onucleus. In some 

 of the Metazoa they form a mantle of long fibers at the side of 

 the spindle and ai'e di\-id(nl iii(li\idually and (H|ually. According 



THK .lOriiXAI, OF KXL-EKI.MKNTAI. ZOOI.fxIV, \ ()I.. It. NO. 1 



