. Outlines of zoology. Zoology. VOL VOX. 95 the parent colony, and form new free-swimming colonies. In other colonies there are special reproductive cells, which may he called ova and spermatozoa. In V. globator the two kinds of reproductive cells are usually formed in the same colony, the formation of spermatozoa generally preceding that of the ova. Technically the colony may then be described as a protandrous hermaphrodite. In V. aureus the colony is oftenest unisexual or dioecious, i. e. either male or female. But it may be monoecious or hermaphrodite, and is then generally protogynous,
. Outlines of zoology. Zoology. VOL VOX. 95 the parent colony, and form new free-swimming colonies. In other colonies there are special reproductive cells, which may he called ova and spermatozoa. In V. globator the two kinds of reproductive cells are usually formed in the same colony, the formation of spermatozoa generally preceding that of the ova. Technically the colony may then be described as a protandrous hermaphrodite. In V. aureus the colony is oftenest unisexual or dioecious, i. e. either male or female. But it may be monoecious or hermaphrodite, and is then generally protogynous, producing eggs first. Whether in a hermaphrodite or in a unisexual colony, the sex cells appear among the ordinary vegetative units; the ova are distinguishable. Fig. 41.—Volvox globator.—After Cohn. a., Balls of sperms ; b., immature ova; c, ripe ova. by their larger size, the "sperm mother cells" divide rapidly and form numerous (32-100 or more) slender spermatozoa, each with two cilia. In V. globator their bundles may break up within the parent colony; or, as always occurs in V. aureus, they may escape intact, and swim about in the water. In any case, an ovum is fertilised by a spermato- zoon, and, after a period of encystation and rest, segments to form a new colony. Occasionally, however, this organism, so remarkable a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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