. A text-book of invertebrate morphology. Invertebrates. 32 INVERTEBRATE MORPHOLOGY. macro- nor microspores develop directly but further develop- ment is contingent upon the conjugation of a micro- with a macrospore. In this respect considerable interest attaches to Volvox; certain cells, usually those situated in the posterior hemi- sphere, enlarge and project into the interior cavity, dividing. Fig. 16.—1. Phacotus lenticularis; 3. Macrospores and Microspores op THE SAME Species (after Butschli). sch = shell. n = nucleus. when they have reached their full growth into a number of cells which
. A text-book of invertebrate morphology. Invertebrates. 32 INVERTEBRATE MORPHOLOGY. macro- nor microspores develop directly but further develop- ment is contingent upon the conjugation of a micro- with a macrospore. In this respect considerable interest attaches to Volvox; certain cells, usually those situated in the posterior hemi- sphere, enlarge and project into the interior cavity, dividing. Fig. 16.—1. Phacotus lenticularis; 3. Macrospores and Microspores op THE SAME Species (after Butschli). sch = shell. n = nucleus. when they have reached their full growth into a number of cells which arrange themselves in a hollow sphere forming daughter colonies in tlie interior of the parent. In addition to this a sexual process occurs ushered in by certain indi- viduals gradually enlarging, and leaving their position at the surface of the colony. In the interior some of them continue to enlarge, forming ova (macrospores), while others divide frequently, forming packets of elongated cells furnished with flagella; these may be termed spermatozoa (microspores). The ova develop into colonies similar to the parent after conjuga- tion with spermatozoa. Since many of the cells of the parent colony do not participate in this reproductive act, but disin- tegrate and die on the development of the daughter colonies, it is clear that we have in this form a rather marked differ- entiation of the individuals of the colony, the individualities of the constituent cells being to a slight extent merged in the individuality of the colony. In NbcHluca in addition to simple division a process of reproduction occurs which partakes of the character of budding. It is apparently pre •. 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 McMurrich, J. Playfair (James Playfair), 1859-1939. New York, H. Holt and Company
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