Ix INTRODUCTION. 



A delicate layer of protoplasm derived from this plexus 

 surrounds the "brown hody""^; and^ indeed (according 

 to Joliet)^ the envelope which immediately incloses its 

 granular contents is formed at the expense of this layer. 

 It is from this protoplasmic covering, and not from the 

 substance of the " brown body " itself, that the bud 

 really originates ; the case therefore enters into the usual 

 order of development. In support of this view, Joliet 

 asserts that the bud is always separated from the "■ brown 

 body " itself by the membranous envelope, and is not 

 in connexion with its substance ("Woodcut, fig. xx\i.) ; 

 but he adds, " II n'est certaintment pas toujour s facile 

 de decider- si c'est aux depens du corps brun lui-meme ou 

 aux depens de cette couclie protoxAasmique que se forme 

 cette ' saillie de matiere granuleuse ' qui est Vorigine du 

 bourgeon." It certainly must be very difficult to decide 

 the poiut; and in the absence of any suspicion that 

 a tissue adequate to the formation of the polypide was 

 present in the neighbourhood, an observer would almost 

 inevitably refer the bud to the so-called germ-capsule as 

 its source. Joliet's researches, showing that the endosarc, 

 by which the brown body is more or less surrounded, is 

 such a tissue, materially alter the case, and prove that 

 the appearances upon which I relied may possibly be 

 susceptible of a different explanation. At the same time, 

 I must add that the bud in the cases referred to always 

 seemed to me, after careful examination, to be directly- 

 continuous with the " brown body," an uninterrupted 

 growth out of it, as represented in my figures. 



Secondly, what is the relation of Eepiachoff's observa- 



* Ehlers had previously described the "brown body" in H(/i)opJwreUa as 

 enveloped by a pnifoplasniic substance, op. cif. p. 1111 



