21 
malige Teile des Organs darstellen. Das erstere erscheint als das 
wahrscheinlichere. 
Wenn sich, wovon ich überzeugt bin, die Mycetomnatur der Pyro- 
somenleuchtorgane bestätigt, wird damit der Symbiontenforschung ein 
neues interessantes Gebiet eröffnet, das eine Anzahl weiterer Fragen 
im Gefolge hat. 
5. Note on the Number of Chromosomes in the male Daphnia pulex. 
By Monica Taylor S.N.D. 
(College of Notre Dame, Dowanhill, Glasgow.) 
(With 9 figures.) 
eingeg. 30. Mai 1914. 
The determination of the number of chromosomes in male Cladocera 
is of great interest in view of the methods of reproduction obtaining in 
this group. As is well known from W eismann’s! researches, the winter 
eggs, which require fertilization, produce two polar bodies, while the 
eggs which develop parthenogenetically produce but one. In a recent 
investigation Kühn? showed that the latter eggs contain, as was to be 
expected, the somatic number of chromosomes. Owing to the great pre- 
ponderance of females over males in this group, however, it is probable 
that the eggs examined were destined to develop into females, and so 
the occurrence of special cytological processes in the maturation of the 
parthenogenetic eggs destined to develop into males is not excluded. 
The most important thing to establish at the outset is whether the male 
has a diploid number of chromosomes or a haploid (as in male Hymeno- 
ptera produced parthenogenetically). 
With a view to determining this question, Dr. Agar collected over 
the course of a few years, males of various species of Cladocera, a pre- 
liminary examination of the somatic and spermatogonial mitoses of which 
had shown the probability that the number is diploid. This material 
Dr. Agar handed over to me for more detailed examination. 
The only part which proved suitable for detailed work was Daphnia 
pulex, of which the collection contained a number of males of recorded 
ages, from 24 hours to 6 days and upwards. The majority of these spe- 
cimens had been fixed in Gilson-Petrunkewitch, cut into transverse 
and sagittal sections of thicknesses from 4 to 7 u, and stained in Ehr- 
lich’s and Heidenhain’s haematoxylin, prolonged staining being 
1 Weismann A., 1886, Richtungskörper bei parthenogenetischen Hiern. Zool. 
Anz. Nr. 9. 
2 Kiihn, Alfred, Die Entwicklung der Keimzellen in den parthenogenetischen 
Generationen der Cladoceren D. pulex De Geer und Polyphemus pediculus De Geer.. 
Archiv für Zellforschung 1. Band. S. 538. 
