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JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



producing eggs, the single egg, which is comparable to the single egg of 

 Salpa pinnata or Salpa cylindrica or to the five eggs of Salpa hexagona, 

 is certainly not the ovary, but a true egg which was differentiated from 

 the ovary of the preceding generation. 



This fact was pointed out many years ago by both Huxley and 

 Kowalevsky, and Huxley (Anatomy and Development of Pyrosoma, 

 Trans. Linn. Soc., 1860, XXIII), after showing, p. 212, that each bud 

 carries away one fully differentiated ovum, together with part of the 

 reproductive organ of its parent, says : " It is not a little remarkable that 

 the first recognizable part of the new organism should be the foundation 

 of that structure which will eventually develop into a creature distinct 

 from it." 



Seeliger, in his paper on the origin of alternation of generations in 

 salpa (13), p. 410, denies this fact, and says that in pyrosoma "no eggs 

 except the ones which remain in the body of the mother are recog- 

 nizable before the rudiment of the reproductive organ of the mother 

 is differentiated from the mesoderm of the future buds ; and that the 

 eggs of following generations of buds are differentiated later." 



I appeal, however, to Seeliger's own figures of pyrosoma (15) pub- 

 lished a year later, and especially to his Taf. XXXII, Fig. 22, which I 

 have copied in cut Z. He says, p. 652, that this figure shows " Die Region 



CUT Z. 



in welcher spdter der stolo prolifer zur Ausbildung gelangt," and he 

 represents clearly, in addition to the egg marked o (ovum), which is 

 destined to be fertilized in this individual, two others, marked ms 

 (mesoderm), which are destined to pass " spater " into the stolon in order 

 to undergo their development within the bodies of future buds which do 

 not yet exist. 



