130 
Alice Borin«' 
mining chromosome raust be present in about half of the spermatozoa 
or of the unfertilized eggs. So we must assume that the small chro- 
mosome in Ascaris is united to the eud of oue of the long chromo- 
somes iu enough eggs to make it present in half of the fertilized eggs of 
every worin; that it comes onl}’ from the male prouucleus 'as there 
are many cases where it is proved to come from the male, and only 
oue where it seemed to be proved to come from the female) and 
that it is attached to oue of the loug chromosomes during the entire 
spermatogenesis except in one ar two rare instances. There can be 
110 doubt that the small chromosome in Ascaris is sometimes due to 
fragmentatiou, and it is possible that in the other cases it is a sex- 
determining heterochromosome. However this latter hj'pothesis in- 
volves so many assumptious, that if we adhere closely to the facts 
observed and assume nothing, we shall have to leave the question 
iinsettled for the present, and hope that more material and further 
study will answer it more detinitely in the future. 
Bibliography. 
Boveri, Th. ’87. Zellenstudien I. Jena 
‘88. Zellenstudien II. Jena. 
m . III. 
‘99. Die Entwicklung von Ascaris meg. mit besonderer Rücksicht auf die 
Kernverhältnisse. Festschr. f. C. von Kupffer. 
'04. Ergebnisse über die Konstitution der chromatischen Substanz des 
Zellkerns. Jena. 
Fürst, E. '97. Über Centrosomen bei Ascaris meg. Arch. mikr. Anat. LI. 
Herla. 0. ‘94. Etüde des Variations de la Mitose chez l’Ascaride megalocephale. 
Arch. de Biol. XIU. 
Mc Clung, C. E. ’05. Chromosome Complex of Orthopteran Spermatocytes. Biol. 
Bull. IX. 
.Mever, 0. ’95. Cellulare Untersuchungen an Xematodeneiern. Jen. Zeitschr. f. 
Naturw. N. F. XXH. 
Montgomery, T. H. 08. On the Morphological Diflerence of the Chromosomes 
of Ascaris meg. Arch. f. Zellforschung. II. 
ZojA, R. ’95. Sulla indipendenza della cromatina paterna e materna uel nucleo 
delle cellule embrionali. Anat. Anz. XI. 
Explanation of Plate X, 
All of the figures refer to generative cells of Ascaris megaloccphala. Figs. 3, 
4, 20 and 21 are from univalens, Figs. 5 and 6 from bastards between univalens 
and bivalens; all the other figures are from bivalens. 
