ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
491 
of the larval tentacles, is erroneous, so far at any rate as Cassiopea 
xamachana is concerned. The beginning of the formation of the 
rhophalium is marked by the appearance of otoliths which arise as 
glistening white bodies in the tentacle, just beyond the apex of the 
marginal lobe. A little later a slight elevation is noticeable on the 
aboral side of each rhopalial tentacle, immediately external to the mass 
of concretions. The epithelium at this point is pigmented, and forms 
the first rudiment of the eyes. As the marginal lobe grows, a process 
is formed on each side of the tentacle, and a ridge on the aboral side 
connects them. These processes finally form the rhopalial lobes of the 
umbrella, and the connecting ridge grows out over the rhopalium as the 
hood. At length a stage is reached in which, while the distal part of 
the rhopalial tentacle retains its structure and is completely functional 
as a tentacle, its basal portion is a well-developed rhopalium ; in this 
latter the differentiation of the ectoderm into sensory epithelium, eye- 
spot, and nerve-fibre-layer is complete. The next stage in the develop- 
ment of the rhopalium is the absorption of the distal portion of the 
tentacle, and when the stump is finally absorbed there is a fully formed 
rhopalium with a thick layer of nerve-fibres and a cup-shaped ocellus. 
Reproduction by Budding in Discomedusae.* — Mr. R. P. Bigelow 
considers that in such cases as have already been reported budding 
appears to be merely an incident in the life-history of the individual. 
In Cassiopea xamachana it is an important if not the chief factor in the 
perpetuation of the species. The bud appears as a slight swelling on 
the body of the scyphistoma near the stem, and involves all three layers 
of the body ; as it grows the opening between it and the coelenteric cavity 
of the scyphistoma is gradually closed by a constriction. The constric- 
tion increasing, the bud becomes set free as a pear- or spindle-shaped 
ciliated body. This mode of budding is probably the most highly 
specialized of those as yet known ; it seems to be an especial adaptation 
to overcome the unfavourable effect on the distribution of the species 
caused by the sedentary mode of life of the adult, a mode very unusual 
with Medusae. As it dwells on the bottom in quiet lagoons and bays, 
its eggs stand little chance of wide distribution, and the planulae would 
probably not swim very far from their mother before becoming fixed. 
The individual buds probably do not swim very far either, but the last 
of a series of generations of buds may be at a great distance from the 
parental, sexually produced scyphistoma. 
Siphonophore from Plymouth. f — Mr. J. T. Cunningham has a note 
on a Siphonophore which was found in great abundance close to Ply- 
mouth breakwater in September 1891. He calls it Muggisea atlantica , 
and shows how it is to be distinguished from M. Kochi Haeckel, of which 
M. pyramidalis and M. primordialis are stages. 
Dendroclava Dohrni.| — Hr. R. Zoia describes some specimens of 
this hydroid. He agrees with Weismann, its original describer, in 
assigning it to the sub-family Pandaeidae of the Tiaridae, but he points 
* John Hopkins Univ. Circ., xi. (1892) pp. 71-2. 
f Journal Marine Biol. Ass., ii. (1892) pp. 212-5 (2 figs.). 
+ Boll. Scientif., Nos. 3 and 4, 1891. See Ann. and Mag. Nat. Hist., tx. (1892) 
pp. 409-11. 
