86 ACALETIIS IN GENERAL. Part I. 



■\vliicli is gradually ciilari:;e(l ami elongated and from Avliicli hang all tlie other 

 secondary l)ud,s, and the secondary Ilydriv, Avhich are more or less similar to one 

 another and remain small through lite. 



The next step in the complication of these communities consists in the appear- 

 ance of other kinds of" Medusaj and other kinds of Ilydroids, variously combined 

 in diflerent genera : the additional Medusae being genuine sexual Medusfie, and the 

 additional Ilydroids partaking also, more or less, of the character of Medustc. A 

 comparison of these sexual Medusa; Ijuds of Siphonoplior;v Avith the Medusa^ buds of 

 ordinary Ilydroids must satisf)- any one, equally familiar -with tlie mode of develoj)- 

 ment of the two tyi)es, that there is no essential difference ))et\veen them. The 

 illustrations published ]>\ Kiilliker in the " Sclnvinniipolypen " (PL VIII. F/'i/s. 4 and 

 5) afford the best example on record for a comparison Avith FiffS. 13, 14, 15, 

 and l(j of PI. XVIII. of this work. Fii/. 4 of Kolliker represents Avhat he calls 

 the testis of Vogtia pentacantha ; it is the exact counterpart of my F/'[/s. 13 and 14, 

 which represent a male Medusa of Coryne mirabilis. KoUiker's Fir/. 5 represents 

 what he calls the ovary of the Vogtia; it corresi)onds exactly to my Fit/s. 15 

 and 10, which represent the female Medusa of Coryne. Now this so-called testis 

 and this so-called ovary consist of a genuine INIedusa Ijcll, with lour radiating 

 chymiferous tubes and a circular tuljc, identical in their structm-c and arrangement 

 with the cliymiferous tuljcs of all the naked-ej'ed Medusa\ The resem)>lance extends 

 even further : KoUiker's Ft'//. 4 shows distinctly the proboscis of this supposed testis ; 

 it is mai'ked e in his figure and described as sperm sac, and its vil)ratile cavity 

 is marked d. The proboscis of the suppo.sed ovary is not less distinct in F/'i/. 5; 

 it is marked r, and descriljcd as an egg sac. But had Kolliker examined more 

 fully these prominent sacs arising from the centre of tlieir Medusa^ l)ells, he would 

 have satisfied himself that the sperm cells and tlie eggs are not contained in the 

 cavity of tlie sacs, but arise, as the eggs and s})erm cells of the Coryne, in the 

 outer wall of the sacs; that is, upon the prol)oscis of the Medusa^, as in Coryne 

 and a large numlier of other genera of naked-eyed Medusa\ 



The second kind of secondary Ilydra^, upon the actinal prolongation of the axis 

 of the i)rimary Hydra of many Pliysophorida', differs from those already described 

 in having a so-called covering scale (Ucckblatt, IIydroph_\llium) by the side of their 

 pendent proboscis. As 1 have already shown (pp. 54 to 50), this is a kind of open 

 bell, intermediate in its character between the calyx of an ordinal y Hydroid and 

 the bell of an ordinary IMedusa, more medusoid than the calyx of a Ilydroid but 

 less so than a Medusa proper, having no radiating chymiferous tubes, and differing 

 from l)Dtli in being one sided and more or less flattened. But as one-sided calyces 

 occur also among Ilydroids, this does not constitute an important difference, nor 

 a distinguishing feature for Siphoii()](liora\ 



