188 
George Arnold 
tropic chromosome iu tlie species Archiineriis calcarator and Bmiasu 
calva. (’05 and ’07). 
Under tlie circumstauces, and in view of Foot and Strobell’s 
revision of Anasa tristis, one cannot lielp suspecting that in Archi- 
»lerus and Banasa the so-called heterotropic or accessory cbromo- 
some is really a nucleolus. 
The 2nd. meiotic division. 
In tlie prophase of tliis division tlie cbromosomes derived froni 
tlie Ist. maturation division are rapidly sorted out. Tbey are closely 
compacted togetber in tlie telopbase of tbe Ist maturation division, 
and very little liuin is visible (Fig. 25). However, as tbey separate 
apart, tbe liuin becomes niore distiiict ^Figs. 26 — 29) ouly to dis- 
appear agaiu on tbe formation of tbe spiudle (Fig. 30). Tbe very 
distinct spiudle-rest, derived froin tbe previous division, takes acid 
staius ratber strongly. It bas not beeu possible to see if tbe centro- 
somes arise from tbis body, but by tbe time tbe spindle is just 
forming (Fig. 30) it bas become cousiderably smaller, and a little 
deuser, disappearing altogetber wben tbe cbromosomes are on tbe 
equatorial plane (Fig. 31). 
In a large uumber of polar, and iu some of tbe side views of 
spindle figures, is is possible to distinguisb tbe micro-cbromosome 
(in Fig. 31). As iu tbe previous division, it lags bebiud tbe otbers 
wbeu dividiug, but iu tbis case, very mucb more so. 
Wbeu all tbe otber cbromosomes bave reacbed tbe poles, tbis 
micro-cbromosome bas ouly just beguu to divide (Figs. 32 and 34). 
Figs. 35 — 37 illustrate tbe telopbase. 
Here agaiu, tbe spindle-rest is very conspicuous, but instead of 
becoming fainter and smaller, it becomes denser, takiug tbe acid 
staius very strongly. It acquires a membraue and elongates. Figs. 
30 and 40 sbow it iu two spermatids iu longitudinal and transverse 
section, and eveutually it euters iuto tbe composition of tbe Sperma- 
tozoon tail and middle piece. 
Summary. 
Hydrophilus bas 30 spermatogouial cbromosomes, wbicb are 
paired in tbe Ist. meiotic propbase to form 15 gemiui. 
In tbe Ist. meiotic division, in additiou to tbe 15 gemini, tbere 
is auotber body wbicb is tbe uucleolus. 
