DENDEOSOMA KADIANS 



BY J. LE%1CK. 



Read before the Society Deceinhey 16, 1879. 



lu briugiug under your notice Dendrosoma radians, I cannot claim 

 for it the beauty of colour, form, and motion, of those tiny spheres of 

 revolving vegetable life known to us all as Volvox [ilohator; nor do I 

 promise you that pleasure which most microscopists feel in watching the 

 dehcate ciliary action and tracing the wondei-ful internal organisation of 

 the Eotifera or Polyzoa. But I can recommend it as an object worthy 

 of careful observation, gaining in interest the more perfectly its life- 

 history is made out, and one that serves, perhapo better than any 

 other, to give a general idea of a curious family of microscopic creatures, 

 the Acinetina, of which many forms have been exhibited at our 

 meetings, and of which specimens of one kind or other are to be found 

 in nearly every pond and stream. From some cause or other, this 

 organism seems to have escaped that careful study, given to many of 

 its allies, which is necessary to make out its economy and Ufe-history. 

 Whether this arises fi-om the rarity of its occmi-ence, the difficulty of 

 observation, or its apparent lack of interest, I am unable to say, but I 

 have felt, as have probably many others, that the descriptions in the 

 books we have at our command are meagre and unsatisfactory, and, as 

 far as I have been able to observe, often incorrect, no figiu'6 even being 

 given in any English work. 



In the case of Dendrosoma, as in that of a large proportion of the 

 known microscopic forms of animal and vegetable hfe, Ehrenberg 

 appears to have been the first to note and record its existence. Subse- 

 quently, Stein and others have given it more or less attention, but 

 ■with the result that it is stLU left in an uncertain position, no satisfac- 

 tory conclusion ha\"ing been arrived at as to whether it is a real species 

 or a mere stage in the development of some other Infusorian, as 

 Vorticella or Vaginicola. In fact, the whole genus of Acineta is scarcely 

 free from a similar doubt in the minds of some observers, although 



Eefeeences to Plates I. and II. 



Fig. 1. — Dendiosoma, a fine specimen, x 50 diameters. 



Fig. 2. — „ moving as an Amoeba, x 100 diameters. 



Fig. 3. — „ with testes and early stages of the tentacnlated heads, 



X 220 diameters 

 Fig. 4. — „ showing embryos, x 220 diameters. 



Fig. 5. — „ showing ovary, x 100 diameters. 



Fig. S.— „ a much contracted form, with three probable embryos 



X 220 diameters. 

 Fig. 7.— „ supposed further stage of the series, 4a— 4d, x 220 



diameters. 

 Figs. E and F.— Part of Fig. 4, showing gradual return of the parent to normal 

 form, X 440 diameters. 



Fig. G.— Probable egg, x 440 diameters. 



