8 KARYOKINESIS. 



more densely staining body, usuallj' eccentric in position, Plate I, fig. 1. The chro- 

 matin is in the form of small granules, varying in size and irregular in shape, which 

 are attached to linin threads stretching through the vesicle. Many of these gran- 

 ules can be seen to be three- or four-parted, though others are rounded or irregular 

 in shape. The four-parted granules are larger than the others but all are extremely 

 small ; their method of formation was not observed. At this stage no trace of cen- 

 trosomes can be found anywhere in the egg. 



2. Egg Laying. — After the eggs leave the ovarj^ tliey descend to the lower 

 enlarged part of the oviduct, where they meet spermatozoa from the receptaaduin 

 seniinis and together with an albuminous fluid are surrounded by a glairy, mucous 

 substance, wdiich hardens into capsules. These capsules are attached together in a 

 cluster and are fastened by a common stalk to the object upon which the female is 

 seated. All the eggs laid by one individual begin development at nearl}^the same 

 time and proceed with remarkable uniformity, so that whenever examined they are 

 all found to be in approximately the same stage. 



The earliest stages of free eggs which I have seen were taken from the oviduct 

 while the capsule was being formed. The outline of the egg at such a stage is 

 usually elliptical or irregular, being in marked contrast with the spherical form 

 which it attains after the entrance of the spermatozoon. The germinal vesicle is 

 slightly eccentric in position and immediately around it there is a small amount of 

 cytoplasm in the interstices between the yolk spheres ; elsewhere in the egg the yolk 

 spheres are closely crowded together. The nucleolus is now a single, homogeneous 

 body and frequently exhibits an alveolar or recticular structure. The chromatin 

 granules are rounder and a little larger than in the ovarian egg and many of them 

 are arranged in rows or strands, fig. 2. In one egg of this stage I observed two 

 minute granules in the cj'toplasm, close to each other and in contact with the 

 nuclear membrane ; these are possibly the centrosomes, though no polar radiations 

 or central spindle was observed. At this stage the spermatozoon has not entered 

 the egg (Plate I, fig. 2). 



B. Maturation Divisions. 



1. Nucleus. — The earliest trace of the first maturation division which I have 

 seen appeal's about the time of the entrance of the spermatozoon. The centrosomes 

 are now plainly visible, being surrounded by a few short radiations, and are connected 

 by a central spindle. At the same time the nuclear membrane is indented opposite 

 the poles of this spindle and fibres can he traced from the centrosomes to these 

 indented areas, Plate I, figs. 3 and 4. 



At this stage the germinal vesicle contains a great number of chromatin granules 

 which are connected together by linin threads, also a single extremely large nucleo- 

 lus, while the nuclear sap fills all the interstices within the nucleus and constitutes 

 the greater part of its bulk. 



(a). Chromatin. — A few of the chromatin granules are larger than the others 

 and their form is spherical, 2-lobed, 3-lobed or 4-lobed. They are probably identi- 

 cal with similar granules found in the pre-division stages. They differ much in 



