. Carnegie Institution of Washington publication. 14 Papers from the Department of Marine Biology. The roots of the peripheral part of the system (text-figure GB) show two well-marked differences. The first of these I have already men- tioned, namely, the smaller size of the yolk globules indicating that consumption rather than accumulation of food stores is the physio- logical condition in this region. The second is the occupation of the lacunar space by masses of small rounded nuclei with a scanty cyto- plasmic investment. The external layer is, on the other hand, free from nuclei, which thu
. Carnegie Institution of Washington publication. 14 Papers from the Department of Marine Biology. The roots of the peripheral part of the system (text-figure GB) show two well-marked differences. The first of these I have already men- tioned, namely, the smaller size of the yolk globules indicating that consumption rather than accumulation of food stores is the physio- logical condition in this region. The second is the occupation of the lacunar space by masses of small rounded nuclei with a scanty cyto- plasmic investment. The external layer is, on the other hand, free from nuclei, which thus appear to have migrated internally. The origin of this lacunar tissue must be looked for in the external syn- cytium. Its function is undoubtedly reproductive; it accumulates particularly as the end of the rootlets which give rise to external FIG. 5. Thompsonia parasitic on Synalpheus brucei, showing mature external sacs springing from a tail fan of the host. One is full of mature Cypris larvae. In the other the larvae have mostly escaped through the apical aperture, ap. The root system, r, is remark- able for the large number of internal buds, cl., none of which are advanced in development. At an. anastomosis of two branches may be seen. The external sacs have recently under- gone a moult and the remnant of the chitinous envelope, ch., is seen around the peduncle. Fixed in Flemming's fluid. X35. ap It will be well now to consider the terminal swellings of the rootlets (text-figure 4s). These are formed by the development of the exter- nal syncytial layer as well as the enlargement of the lacuna within. The external layer increases in thickness and the nuclei become much more numerous, migrating superficially, taking up a position with their long axes at right angles to the border. In fact, the tissue tends to assume a regular epithelial structure. Internally the protoplasm contains numerous yolk globules of various sizes and nuclei are rare and sparse. The interior la
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