Potts, Frank A. (1913). Stolon formation in certain species of Trypanosyllis.. Quarterly Journal of Microscopical Science, London. 58(3): 411-446.

62944

Potts, Frank A.

1913

58(3): 411-446

Publication

http://jcs.biologists.org/content/s2-58/231/411

Kristian Fauchald's Polychaeta DB

In several species of Trypanosyllis the stolons are produced from a cushion of proliferating tissue at the posterior end of the stock in successive transverse rows of seven or eight, the number produced by a single individual being between one and two hundred. New rows are established at the anterior end pushing those already formed backwards so that the oldest stolons are most posterior. Ectoderm and mesoderm alone take part in the formation of the stolons so that they are without an alimentary canal. Two slightly varying types of the phenomenon have been distinguished in the two species here studied. The following divisions correspond roughly to the stages observed in the growth of stolons. In no example was it possible to examine the early formation of the proliferating cushion. (1) The aggregation of leucocytes in the posterior segments, which invade the mesoblast of the proliferating cushion. (2) The appearance of centres of proliferation in the epiblast, which cause the formation of stolons. The mesoblast advances and fills the hollow processes formed by the ectoblast. It lies at first in close association with the ventral surface of the stolon. (3) The mesoblast of the stolon proliferates and segments. The first appearance of segmentation is the formation of septa. (4) The invasion of the stolon by two bundles of muscle-fibres in direct continuation with those of the stock, and a single ventral nerve-cord, also an outgrowth of the corresponding structure in the stock. (5) The segmentation of the epiblast of the stolon and the formation of the structures derived from it (setæ, etc.). The gonads are formed as lateral outgrowths from the central mesoblastic mass. With the growth of the stolons the proliferating cushion is gradually absorbed.

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