ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



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distinguishes a primitive stem (A), without hydrocladia, with a naked 

 basal region and a region with cauline hydrothecae. When the 

 hydrocladia begin to be formed, the colony has, for a time, a transitory 

 stem (B) in which may be distinguished a basal region (Rb), a 

 hydrocladial region (Rh), and an intermediate region (Ri), the cauline 

 joints of which bear hydrothecae. The definitive stem (C) is characterized 

 by the disappearance of cauUne hydrothecae. The joints of its inter- 



A B C 



Diagram of three stages in the development of the stem of Aglaophenia. 



mediate region bear nematothecas only. The figure shows the typical 

 architectonic scheme for a colony arising from a larva and not arising 

 by budding from a hydrorhizal stolon. Modifications of the scheme 

 may arise in various ways. J. A. T. 



Variations of Aglaophenia pluma. — M. Bedot {Revue Suisse 

 Zool, 1919, 27, 243-82, 27 figs.)- An interesting study of this 

 Plumularid, showing the variations (or observed differences) in facies, 

 size, hydrorhiza, stem, nematothecae, hydrocladia, hydrothecae, gonosomes, 

 and so on. The species is re-defined on a broad basis of investigated 

 form, three varieties are established, and the relation of A. pluma to 

 related species is discussed. J. A. T. 



Pcrifera. 



Remarkable Phenomenon in Gemmule Cells of Fresh-water 

 Sponge.— H. van Trigt (Arch. Neerland. Physiol., 1918, 2, 594-603, 

 3 figs.). The turgescent cells of the gemmule of Spongilla are seen 



