78 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tomous and anastomosing filaments. Up to the present time it has 

 never been recorded again. The authors of the present paper have 

 however found it among the material collected in the Dutch East 

 Indies by the Siboga expedition, and have been able to prove that the 

 supposed anastomosis of the filaments does not exist. The anastomosis 

 figured and described by Montagne takes place — not indeed between 

 the filaments, but between the lines of calcareous cement, which fills 

 the grooves between contiguous filaments. Montagne made his draw- 

 ings and observations from calcified specimens, and mistook the dark 

 lines of calcification for the filaments of the thallus ; these latter 

 appearing in a calcified plant almost transparent by contrast with the 

 opaque connecting lines of calcium carbonate. The presence of anasto- 

 mosis between the filaments having been disproved, the genus cannot 

 be maintained. Rhipidosiphon is nothing but a simple Udotea, and \i 

 here placed in that genus under the name of U. javensis. Gallipsy^ma 

 has only been found once, at Port Phillip, Victoria ; and half of the 

 original plant is preserved at Lund, while half is in the British Museum. 

 It is here figured for the first time, and further details are added to our 

 knowledge of its structure. The stipe is two-edged, uncalcified, and 

 throws out at the margins coinplanate rachides, which grow out each 

 into a terminal flabellum. The whole plant is complanate and uncal- 

 cified, and bears no resemblance to Rhipocephalus, with which genus it 

 has been compared. The plant appears to be transversely septate, but a 

 careful examination under high magnification shows that the septa are 

 perforated, and are in fact nothing but thick rings of cellulose which 

 have grown inwards from the sides, similar to the plugs or stoppers in 

 Godwin and other allied genera. Figures are given of the two genera 

 described. 



Oogenesis in Vaucheria.* — B. M. Davis has made a minute study 

 of this phenomenon in Vaucheria geminata var. racemosa, and comes to 

 the following conclusions. The number of nuclei in the young oogonium 

 ranges from twenty to fifty. There are no mitoses in the oogonium. 

 It becomes separated from the parent filament by a cross wall, and is 

 multinucleate at the time the cross wall is formed. Even before this 

 wall is complete, a process of nuclear degeneration is evident, and it 

 continues until only one nucleus remains in the oogonium. The 

 degenerating nuclei are found chiefly in the periplasm. They become 

 exceedingly small, the nuclear membrane disappearing first, and finally 

 nothing remains but granular matter, apparently nucleolar in nature. 

 There is apparently no ccenocentrum in the e^ of Vaucheria, but the 

 surviving nucleus lies at the centre of the oogonium. The e^ nucleus 

 grows rapidly until it is three or four times the size of the nuclei in the 

 young oogonium, and there is a marked increase of chromatin. After 

 fertilisation the nucleus of the sperm passes to the centre of the egg 

 and increases in size, at the side of the female nucleus. The two fuse 

 slowly when both are of approximately the same size. The process of 

 oogenesis in Vaucheria agrees in a striking manner with that in Sapro 

 lecjnia and the Peronospomles. The paper ends with a discussion of the 



* Bot. Gazette, xxxviii. (1004) pp. 81-98 (2 pis.). 



