. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NORMAL DEVELOPMENT IN ZOOTHAMNIUM ALTERNANS 123 position and continues as before, giving origin to :1 (lateral) and 3jc2 (median); to 4*1 and 4jt2, etc. Each time the alternate secondary daughter is left behind as a common zooid (Fig. 1). Further mitotic activity in the common branch zooids 2x2, 3xz, 4#2, etc. was not characteristic of the normal colonies whose histories were charted. About 2 per cent of the total number of colonies under surveillance showed a tendency toward precocious development. In these cases th
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NORMAL DEVELOPMENT IN ZOOTHAMNIUM ALTERNANS 123 position and continues as before, giving origin to :1 (lateral) and 3jc2 (median); to 4*1 and 4jt2, etc. Each time the alternate secondary daughter is left behind as a common zooid (Fig. 1). Further mitotic activity in the common branch zooids 2x2, 3xz, 4#2, etc. was not characteristic of the normal colonies whose histories were charted. About 2 per cent of the total number of colonies under surveillance showed a tendency toward precocious development. In these cases the repeated divisions of all branch zooids led to such complex formations that the lineage soon became impossible to follow. Conversely, microzooid \X on branches up to about level J com- monly divides once, forming \Xi (median) and IX2 (lateral). Its mitotic activity on more distal branches is infrequent. On several Presumptive Ciliospores. FIG. 3. Schematic representation of branch development. branches of each colony the cell IX or its descendants metamorphose into the migratory ciliospores which break away from the parent colony, leaving behind a short, stubby peduncle. Occasionally IX produces a second or sometimes a third generation thereby augmenting the number of propagatory zooids. DIFFERENTIATION The distribution of the heteromorphic zooids to be described is a generalized account based upon a tabular evaluation of 200 cases of normal and experimentally cut colonies (proximal portions only), many of which were lost before complete development. Inclusion of the basal parts of operated colonies in the tabulations seems to be justified since statistical summaries of both normal and operated. 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biolog
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
