Chromosomes in Living 07ganisms. 301 
a Fern, is supported by the fact that apospory also occurs 
among Ferns. In certain varieties of Atkyrium , Polystichum , 
and Aspidium , as F. O. Bower has shown 1 , fertile prothallia 
are developed in place of sporangia. It would appear, there- 
fore, that the nuclei of these prothallia must contain twice 
as many chromosomes as do those of normally developed 
prothallia ; and consequently, since no reduction in the 
number of the chromosomes occurs in connexion with the 
development of the sexual cells, these cells would, in this 
special case, contain twice the normal number of chromo- 
somes. It is, however, more reasonable to assume, until 
direct observation proves the contrary, that the aposporous 
development is attended with a correlative reduction in the 
number of the chromosomes. On similar grounds it is probable 
that a reduction also attends the development of protonema> 
eventually bearing sexual plants, which has been induced in 
the sporogonia of certain Mosses. From the fragments of 
setae of species of Hypnum and Brynm , Pringsheim 2 obtained 
the development of protonema ; as did also Stahl 3 with Cerato- 
don purpureus , not only from cells of the seta but also from 
those of the wall of the capsule. It is probable that in this 
protonema a reduction of the number of the chromosomes 
takes place under the influence of correlative processes. 
The foregoing phenomena suggest the raising anew of the 
question as to the continued independent existence of the 
chromosomes. In the case of plants it may not be con- 
sidered as settled that, in the resting nucleus, the chromo- 
somes present no free ends. Guignard 4 , whose statements 
are perfectly correct 5 , found but a single filament at the 
beginning of the prophase in the nuclei which he examined. 
1 On Apospory and allied phenomena, Trans. Linn. Soc., Ser. Bot., Vol. ii, 
Part 14, p. 301, 1887. 
2 Ueb. vegetative Sprossung der Moosfriichte; Monatsber. d. Berl. Akad. d. 
Wiss., June io, 1876. 
3 Ueb. kiinstlich hervorgerufene Protonemabildung an den Sporogonien der 
Laubmoose, 1876. 
4 Nouvelles Etudes, p. 253. 
5 Strasburger, Schwarmsporen, Gameten, &c., Histol. Beitr., Heft IV, 1892, 
P- T 47 * 
