ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
699 
even though very closely allied organisms, as may be seen from the 
following table : — 
In Polar In Cleavage 
Spindles. Spindles. 
Ascaris megalocephala (type Van Beneden) .. 1 2 
„ „ (type Carnoy) 2 4 
Coronilla sp ; . .. 4 8 
Spiroptera strumosa and Ophiostoma mucronatum .. 6 12 
Filar oides mustelarum 8 16 
Echinus microtuber culatus and Sagitta bipunctata 9 18 
Tiara sp. 14 28 
Fterotrachea , Carinaria , and Phyllirrhoe .. .. 16 32 
The number of chromosomes in the first is the same as that in the 
second polar spindle. The number formed from the egg-nucleus is similar 
to that of the elements devoted to the egg on the formation of the 
second polar body. As the egg- and sperm-nucleus give the same 
number of chromosomes to the first cleavage-spindle it follows that this 
last has twice as many chromosomes as each polar spindle, and also an 
even number. The generative cells of an organism contain half as many 
chromosomes as the first embryonic cell from which the organism arose. 
There are, it is to be noted, certain irregularities in some of these 
numerical relations, so that a definite number of chromosomes is not 
always characteristic of a species. 
IV. Chromatic Substance in Parthenogenesis and the Significance of 
Polar Bodies.— The author thinks that the best hypothesis to explain 
the phenomena of parthenogenesis is that which regards the polar 
globules as rudimentary ova, and this he calls the phylogenetic or egg- 
hypothesis. When the second polar spindle is not removed it is clear 
that the number of chromosomes in such an egg is the same as in a 
fertilized ovum. He subjects the theories of Weismann and others to 
a close critical examination, and finds that facts which destroy the 
value of their hypotheses add strength to his. 
Accessory Corpuscle of Cells.* — Dr. Emma Leclercq has made an 
investigation on the accessory corpuscle of the spermatic cell in which 
great attention w r as paid to the mode of fixation. She comes to the 
conclusion that these cells are more complicated than has hitherto been 
supposed. As a rule, they may be considered to be cells with two nuclei 
—the chromatic nucleus or nucleus of authors, which she calls passive, 
though not in a physiological sense, and the “ Nebenkern ” or accessory 
corpuscle which is the active nucleus and corresponds to the archiplasm 
of Boveri, The latter is a constant element of cells, and plays an 
important part in the spermatozoon, where it very probably forms the 
fibrillar axis of Braun, Jensen, and Ballowitz. There is a chromatic axis 
which is surrounded by achromatic fibrils, while the true nucleus, which 
is here and there traversed by the axis, forms for it a second envelope 
in that region which is called the head. This last is preceded by a 
procephalic achromatic portion which is derived from the accessory 
corpuscle. 
* Bull. Acad. Roy. Belg., lx. (1890) pp., 137-48, 
