GONOPHORES 357 



interesting observations on older examples of Rhizophysa and Physalia which apparently lead to an 

 explanation of the place of origin, previously unknown, of the female germ-cells. According to him the 

 structures previously regarded as male gonophores are undifferentiated germ-tissue, which only later, 

 and in different specimens, develop into male and female germ-cells. In my oldest examples these 

 transformations minutely described by Steche were not observed'. Actually, Richter figured 

 (Taf. XXVIII, fig. 25) what is obviously a section of one of these female gonophores, that he took to 

 be a stage in the development of a male gonophore. Richter rather ungraciously added that Steche 

 had made no new contribution to the subject of the gonodendron and its appendages. 



Perez (1929) published good figures of the endodermal cells of the spadix of the male gonophore, 

 and drew particular attention to the division of many of the nuclei into two, three or more parts, and 

 to the physiological significance of this phenomenon, namely the control of a 'flux metabolique' 

 between the coelenteron and the developing germ-cells. He gathered together many other instances 

 of this phenomenon, of which the multilobate nuclei of the rete on the ventral radial canal of the young 

 nectophore of Hippopodiids is another. 



Although the complete story of the method of reproduction in Physalia is not yet and perhaps never 

 will be known, some progress has been made, and I have been able to substantiate Steche's work and 

 to extend it. Having cut sections of gonodendra to elucidate morphological points, I found two quite 

 distinct types of gonophores, which matched those sectioned and figured by Steche in 1907. I then 

 examined dozens of gonodendra of all sizes which had been dropped by my laboratory specimens at 

 Lanzarote. I found that I could soon distinguish these two types of gonophores, very often without 

 clearing and mounting stained specimens, and from surface inspection in the light of a tungsten- 

 ribbon lamp, or in optical section only. 



One type (PL XXIII , fig. 5), evidently the male, had a thick cap of germ-cells borne by a relatively less 

 capacious endodermal spadix. The walls of this spadix were relatively thin and not at all or only a little 

 lobulated. The cap of germ-cells, situated as usual in the secondary ectoderm formed by the entocodon 

 (' Glockenkern ') and covering the spadix, consists of very numerous small cells which presumably are 

 spermatogonia. I have not made a cytological study of them. 



The other type of gonophore, which can be recognized at all stages of growth, is presumably the 

 female (PL XXIV, fig. 3). Its endodermal spadix has much larger cells than those of the male type, about 

 7000 in number, and the whole ectoderm of the spadix becomes lobulated. In place of the thick cap of 

 spermatogonia there is a very thin layer of germ-cells in the secondary ectoderm. Selecting one of the 

 largest female gonodendra, I managed to cut one of the small gonophores in half transversely and then, 

 after removing the outer membranes, to dissect out the endodermal spadix, leaving the mesogloea and 

 the thin layer of secondary ectoderm with its germ-cells intact. When stained with Ehrlich's haemat- 

 oxylin and cleared, I found to my astonishment that the germ-cells formed a continuous, narrow, 

 sinuous band, one cell thick and two cells broad, running over the surface (PL XXIII, fig. 4). Rapid 

 inspection of a whole mount showed that the cells had large nuclei containing stained chromatin 

 particles. The polygonal cells measure about 13-14/* in diameter and contain vacuoles. The nuclei are 

 about 11-12/* in diameter. The female gonophores measure up to 17 mm. in length and 0-85 mm. in 

 diameter. 



In the latest stage of development, in both male and female gonophores, I find that the whole 

 manubrium (with the exception of the outer membranes with the pair of linked and branched radial 

 canals) may be drawn out, often inside out, into the lumen of the branchlet (PL XXIII, fig. 6). These 

 masses, curious to relate, circulate freely in the branches and the cavities of the palpons. I have observed 

 this in living gonodendra.* It was this sequence of events that Richter misinterpreted, reversing the 

 * I have already mentioned (page 354) that the palpons can open their tips. 



