84 THE OCEANIC HYDROZOA. 



the spire. I am strengthened in this view by Vogt's statement (p. 51) that when the sacculus 

 (his " banderola") is protruded, " it is accompanied through its whole length by a very delicate 

 muscular filament, which is attached to its inner edge, so that it is hidden completely by the 

 folds of the ' banderola' when the latter is retracted into the capsule." It is true that Vogt 

 figures (fig. 9) the end of the sacculus, which contains the large thread-cells, free ; but as the 

 lining membrane of the involucrum is forced out of the aperture, this may well be the result 

 of pressure. 



In other respects the structure of the adult organ, as described by Kolliker and Vogt, is 

 readily reducible to the type of the young form. The cavity of the base of the involucrum 

 appears to become filled up by vacuolated tissue, so that Kolliker describes the wall of the 

 capsule as consisting of three layers. " Close round the inner cavity (whose outline is 

 never twice alike, and which always presents a sinus towards its apex), in fact, is a granular 

 substance, having the same appearance as the wall of younger capsules, only that a reddish 

 colouring matter is deposited on one side of it. This is succeeded (but on one side only, 

 toward the ape.x) by a conical appendage formed of coarsely vesicular tissue ; and, lastly, the 

 whole is invested by a partly striated, partly vesicular-looking substance, whose extreme point 

 is also coloured reddish" (p. 23). This innermost layer is, I doubt not, the inner wall of the 

 dilated base of the involucrum. If the latter (as it appears to do) gradually grew out into- a 

 cone beyond the sacculus, and tiie endoderm of its cavity became vacuolated, as is so constantly 

 the case in the appendages of these animals, we should have the " conical appendage with 

 coarsely vesicular tissue." And if the ectoderm thickened and altered, it would give rise to 

 the striated or vesicular outer substance. 



The reproductive organs are stated by Kolliker to resemble exactly those of his Agal- 

 ■mopsis (^Agalmd). Vogt's account of their structure and development is not very clear, and, if 

 I may judge by the analogy of other Pliysophoridce, is in many respects not quite correct ; 

 l)ut it tends towards the same conclusion. 



Tiie largest of my PhysophortB was taken in the southern part of the Indian Ocean on the 

 17th of June, 1847. With it I obtained a very small one, not more than one third of an inch 

 long, and one of the same size had been obtained on a previous day (June 7th, 1847). 



In these small specimens (fig. 2) the ectoderm of the stem-like portion of the ccenosarc 

 appeared to consist of longitudinal fibres j^th of an inch in diameter. The lower end of the 

 ccenosarc expanded into a somewhat obliquely set, spheroidal, or elliptical, bulbous enlarge- 

 ment, round which were arranged three hydrocysts, two large and one small, which I took 

 at the time for young polypites. These, which have been described above, were arranged 

 nearly in one plane. Below them were numerous small buds, which appeared to be nascent 

 polypites. Arising from one side of the ccenosarc, just below the pneumatophore, were 

 several rudimentary nectocalyces ; the largest and lowest, one sixtieth of an inch in length, 

 had four straight longitudinal canals united by a circular canal, but its nectosac was not 

 yet open. This is, I believe, the youngest state in which Physophora has yet been observed, 

 as the young form described by Vogt has four large hydrocysts and a polypite with open 

 mouth and long tentacle; however, I confess I can understand neither the figures nor the 

 description of the young tentacular sacs of this specimen. 



I will not attempt to refer my Physophora to any of the species yet described, for I doubt 

 whether it is possible, with our present information, to separate one species of Physophora 



