1 2 C. ISHIKAWA. 



is seen from the pole. The eight single chromosomes are clenrlv t(^ l)e 

 seen lying in the equatorial plane of the spindle. The first yxihv hodv 

 is no more to be seen. Figs. 31, 32, and 33 show the spindle in more 

 advanced stages. In the first two figures the chromatic elements 

 are still very short, but in the last (fig. 33) thev are rather elongated. 

 Figs. 34 and 35 show the stage where the second polar bodA^ has en- 

 tirely separated from the egg nucleus, whicli latter has now accpiired a 

 vesicular f^rm. The four chromatic elements are more or less distinct- 

 ly to be seen in tlie second polar body. 



At the stage between the expulsion of the first a.nd the second pohu* 

 bodies the egg passes out of the oviduct int(^ the breeding sac, so that 

 the first polar body lies outside the egg-membrane, which is formed 

 after its expulsion, and after the penetration of a spermatic cell into 

 the egg, which takes place at the extreme distal end of the oviduct. 

 That in Cnpepoda the first polar body lies outside the egg-membrane 

 and therefore is not to be found in eggs that have come out of the 

 oviduct was first shown by Grohheii'^^ in CetocJiilus and afterwards by 

 31. Niisshaumf^'''^ in many Cirripedce, in which it had been foreseen by 

 Weisniann. 



3. A Comparison of the Rqiening Phenomena 

 in Eijij- and Sperm-cells. 



As is shown in preceding pages the correspondence in the deve- 

 lopment of the egg-cell and of the s])ermatic-cell is nearly as complete 

 as in Ascaris, upon which 0. Hertwiif^'^'' has made a series of very fine 

 observations. I say " nearly as complete," because here the corres- 

 ponding zones are not so easy of comparison together as in the case of 

 Ascaris. We can, however, fallow them in each of the developmental 

 phases, as we shall presently see. 



