No. 3] THALASSEMA AND ZIRPHAEA. 613 



nucleus (PI. XXXII, Figs. 32, 33). The more or less complete 

 fusion of the germ-nuclei extends to the chromatin network of 

 each, which even before the fading of the separating membrane 

 shows dark-staining thickenings (PL XXXIII, Figs. 35, 16). 

 The ingrowing astral fibers now crowd towards the equator, 

 the chromatin (PL XXXIII, Figs. 37, 38), which, by this time, 

 forms a more or less perfect spireme. Intervening strands of 

 a finer and more granular nature (linin .■') are, however, still 

 traceable. With the complete disappearance of the nuclear 

 membrane, the spireme becomes closely compacted in the equa- 

 torial plane (PL XXXIII, Fig. 39). Bead-like swellings occur 

 at regular intervals along the entire length of the thread ; 

 these mark out the chromosomes. By transverse division at 

 these swellings, there result 24 pin-shaped chromosomes, at- 

 tached by their heads to the traction-fibers (one fiber to each 

 chromosome). The whole spireme thus going over into the 

 chromosomes, there is here no bodily casting out of chromatin. 

 The above-mentioned finer strands probably represent portions 

 of the original chromatic reticulum that break down into linin, 

 as claimed by Wilson ('95). 



The subsequent history, the divergence and conversion into 

 vesicles of the pin-shaped daughter-chromosomes, the recon- 

 stitution of the nuclei and genesis of the second cleavage 

 amphiaster (PL XXXIII, Figs. 41-46), does not appear to 

 contain anything worthy of especial remark. At no time was 

 any chromatin rejection observed such as Boveri ('92) has 

 described in Ascaris. 



IV. The Polar Bodies. 



The formation of the polar bodies in Thalassema and the 

 almost invariable division of the first have already been minutely 

 described by Conn ('86). As his researches were limited almost 

 entirely to the living egg, he was unable to follow out the 

 details of the mitotic phenomena. The latter are easily studied 

 in sections. The first polar body divides by a complete and 

 typical mitosis, although in minor details it shows evident signs 

 of degeneration. 



