ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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another by threads ; the fissures are filled up by finely granular proto- 
plasm. These bands become further divided by constrictions or by fresh 
fissures. The final products thus formed, the zoospores, swell up 
and become mutually compressed into regular polygonal plates, the 
peripheral membrane disappearing. Each zoospore has a lateral clear 
spot, where the nucleus is situated, two cilia, and two pulsating vacuoles. 
Portions of the protoplasm remain unconsumed as peri-plasmatic remains. 
The cell-membrane now begins to swell, and is forced inwards by 
the unelastic cuticle, and finally becomes ruptured and detached. The 
zoospores, freed from its pressure, begin to “swarm ’’while still con- 
nected with one another by fine threads, and consequently retaining 
their original position ; they come to rest, surround themselves with a 
cell-wall, and form a regular net. 
In those cells which are destined to form gametes, there is usually 
a strong contraction of the central green layer of protoplasm before 
the division, causing it to form a wide-meshed net interrupted by 
clear spaces, and usually of a yellowish-brown colour. The breaking 
up of this layer is effected in the same way as in the formation of 
zoospores, only that it is carried further, the products, which become the 
gametes, being smaller and completely separated from one another. 
The escape of the gametes is preceded by a swelling of the cell- 
wall, which however affects only an inner layer, while the outer layer, 
with the cuticle, remains unchanged. The outer layer is ruptured, and 
the inner layer projects in the form of a bladder. The mass of gametes, 
situated between the inner layer and the vacuole, then begin to 
“ swarm,” and become freed by the further swelling of the vacuole. 
They then conjugate in pairs. 
The process of division of the protoplasm in the cells of Hydro- 
dictyon of both kinds furnishes a typical instance of free-cell-formation, 
in which the daughter-cells do not, from the first, form a tissuo in 
conjunction with the mother-cell. 
Fungi. 
Phylogeny of Fungi.* — Dr. F. de Tavel points out that in the 
Oomycetes we find a great degeneration in sexuality, which at length 
entirely disappears, probably as an adaptation to terrestrial existence, 
the sporango itself of Peronospora being transformed into a spore or 
conid ; and this occurs also in the Zygomycetes, where the zygo- 
spores of sexual origin are often replaced by azygospores. The Myxo- 
mycetes are allied to the Zygomycetes, in two series, corresponding 
to the types with sporanges and the types with conids. At the end 
of the series of sporangiferous fungi are the Ascomycetes. They are 
related to the Mucorini through the Hemiasci. At the summit of 
the series of conidiferous fungi are the Basidiomycetcs, which are 
again allied to the Zygomycetes through the Ustilaginese and Tilletieas. 
The sporangiferous fungi and the conidiferous fungi form two parallel 
series, often difficult to distinguish externally in their higher forms ; 
both are non-sexual, and are derived from the sexual Zygomycetes, 
which again are allied to the sexual Algse. 
_ * Arch. Sci. Phys. et Nat., xxvi. (1891) pp. 512-5. 
