ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 433 



highly refractive globules ; there is no nucleus. Near the point of 

 insertion of the vibratile cilia is a single large orange granule. The 

 motility of the oospheres lasts as long as that of the antherozoids, 

 and is equally affected by light. 



As long as the oospheres are in motion, the antherozoids display 

 no affinity for them ; but as soon as the oospheres have lost their 

 cilia and come to rest, the antherozoids are attracted to them. They 

 move rapidly round them, finally come in contact v^^ith them, lose 

 their cilia, and become absorbed into their substance. A single 

 antherozoid is sufficient to impregnate an oosphere. 



The fertilized oosphere contains the two orange grannies derived 

 from the male and female elements. It immediately becomes invested 

 with a cell- wall, and begins to germinate the next day, dividing first 

 of all into two cells, one of which is much larger than the other. 



Zoospores which germinate without fecundation, resembling those 

 of Zanardinia, are also probably present. They are found in uni- 

 locular zoosporangia, and resemble the motile oospheres except in their 

 much smaller size. 



Cutleria exhibits in its structure several important variations 

 from the FucaceEe. The antheridia are pluricellular in the former, 

 unicellular in the latter. The oospheres of the Fucacese are immo- 

 tile, and do not contain any orange granules ; except in the latter 

 point they resemble the oospheres of Cutleria after they have come 

 to rest. 



The nearest affinity of the Cutleriaceae appears to be with the 

 Ectocarpacege. Ectocarpus Lebelii and secundus possess antheridia 

 which produce antherozoids precisely resembling those of the Cut- 

 leriaceae and of the Fucacese, and equally incapable of independent 

 germination. They also have plurilocular sporangia exactly like those 

 of Cutleriacese. The plurilocular sporangia of other species of Ecto- 

 carpus and of the Phseosporege generally must be regarded as female 

 organs, and the bodies which emerge from them not as true zoospores, 

 but as motile oospheres homologous to those of Cutleriaceae, which, 

 in default of male organs, germinate without fecundation, offering an 

 example of constant parthenogenesis. The same is also probably the 

 case in the pelagic Cutleria multifida. The unisporous sporangia of 

 Tilopteris, Haplospora, and Scaphospora are evidently homologous with 

 the plurilocular sporangia of Ectocarpus ; their oospheres appear, 

 under certain conditions, to germinate parthenogenetically. 



The occurrence of parthenogenesis normally in the greater number 

 of Phfeosporese, and exceptionally only in the Cutleriaceae, must be 

 regarded as placing this family at the head of the group. 



Endoclonium polymorphum.* — Under this name a new parasitic 

 alga is described by M. Franke. It has been observed only on 

 Lemna gibba, on which it occurs in two forms, one endophytic in the 

 air-cavities beneath the stomata on the upper side of the frond ; the 

 other epiphytic, on all parts of the host. The two forms are con- 

 nected by an imperfect alternation of generations ; but the same 



* Cohn's Beitr. Biol. Pflauzeu, iii. (1883) pp. 365-76 (1 pi.). 

 Ser. 2.— Vol. IV. 2 G 



