Notes ou some Hydromedusae frorn the Bay of Naples. 557 



Moreover, tliese sectious failed likewise to aflorcl nuy evitlence 

 of Weismann's so-called "Keimzone". Whìle eggs are found usually 

 iu greater uumbers in the immediate region of the gonophore buds, 

 as might be uaturally expected, than in other portions, stili they 

 are found in not inconsiderable niimbers at poìnts more or less re- 

 mote from this region, both above and below. 



As a rule the egg cells are found in the deeper portions of 

 the entoderm, tho not unusually they are found to oceur likewise 

 ou the surface as shown in Fig. 3. Occurring in greater numbers 

 iu the region near the origin of the gonophore, and possibly also 

 iuciting its development, they seem to be carried into the bud during 

 its formation and development. It would seem, however, that there 

 is a migration of egg cells directly into the gonophore from ad- 

 jacent portions of the stem, since it hardly seems probable that the 

 large numbers which finally occupy the gonophore could bave ori- 

 ginated in immediate contact with it. Such a migration is well 

 known in many other hydroids and may be accepted as occurring 

 bere, tho no direct evidence of it has been observed in the course 

 of the present research. With the growtli of the gonophore there 

 ì<eems to be a segregation of eggs into groups, or nests, about which 

 there are developed follicular folds of the entoderm, as shown in 

 Figs. 4, 5, in some cases eutirely enclosing them. Others continue 

 to He in dose contact with the entoderm lamella and finally form 

 the superficial layer in the free medusa. 



Development of the Gonophore. 



As already intimated, the gonophore arises as a bud from the 

 side of the stem, or more rarely upon a branch. It is at first in- 

 distinguishable from an ordinary hydranth bud, involving a direct 

 evagination of both ectoderm and entoderm. The presence of eggs 

 in immediate contact with it usually reveals its true character. From 

 the first and throughout its entire development nematocysts are found 

 in the ectoderm and multiplying during development furnish the 

 nematocyst Clusters of the exumbrella of the medusa. In iron hae- 

 matoxylin preparations they stain a deep black during early de- 

 velopment, as may be noted in severa! of the figures. 



At first the gonophore is a simple club-shaped organ, as shown 

 in several of the figures, but soon takes on a typical pear-shaped 

 aspect, as shown in Fig. 5, At about this time there seems to be 

 a cessation of the process of ovariau migration into it and very soon 



MittheiluDgen a. d. Zool. Station zu Neapel. Bd. 16. 37 



