LINVILLE : PULMONATE GASTEROPODS. 233 



bodies may, it seems to me, be due to causes which have nothing to do 

 with the movement of the chromatin. It is a well known fact that the 

 ceutrosome goes through certain chemical phases, in which it does not 

 stain at all by a method which at other times stains it deeply. It seems 

 quite possible that the karyosomes may also have chemical phases inde- 

 pendent of any physical accumulation of chromatin. 



AVhether the chromatin in the resting stage of the nucleus is distrib- 

 uted through the substance of the karyosomes, or whether instead it is 

 distributed through the nuclear sap, as Klinckowstrdm ('97) thinks is 

 the case with Prosthecerseus, I believe Platner is right in saying that 

 chromatic substance is to be found at one period in the resting stage of 

 the nucleus collected in rings about the karyosomes. I have frequently 

 noticed densely staining rings, irregular in outline, surrounding faintly 

 stained karyosomes. My best evidence concerning the points in ques- 

 tion is shown in Plate 1, Figure 6. This figure represents the formation 

 of the first cleavage spiudle, and, quite exceptionally, the two so-called 

 pro-nuclei have fused. Rays from each aster have extended into the 

 substance of the fused nuclei, one bundle of rays running nearly through 

 the nuclei. Scattered along this bundle of fibres are numerous deeply 

 stained, bent rods. Similar rods may be seen here and there in the 

 nucleus, apparently unattached. Still others are found lying very close 

 to the faintly stained karyosomes and in more or less intimate coutact 

 with them. The chromatin particles surrounding the karyosomes, those 

 lying loose in the nuclear sap, and those being drawn along the pene- 

 trating astral rays, are so evidently of the same origin that investigation 

 of the history of the chromatin within the resting nucleus would involve 

 an examination of the changes in the so-called nucleoli or karyosomes. 



B. FERTILIZATION. 



I. The Early History of the Spermatozoon in the Egg. 



1. General Description. 



As I stated at the beginning of this paper, the first evidence of the 

 presence of the spermatozoon in the egg of Limax that I have seen, was 

 in specimens taken from the uterus. Xot only was the first evidence of 

 penetration of the spermatozoon seen in uterine eggs, but in all. uterine 

 eggs that I have examined penetration had taken place. Whenever I 

 have found eggs in the oviduct (L. agrestis), great numbers of sperma- 



