OBSERVATIONS ON BRITISH MARINE AUi.K. * 103 



irregularly from the terminal joints of the finer branches. Tliey 

 are borne on bicellular pedicels, and are accompanied by a branched 

 hair which arises from the distal cell of the pedicel. 



II. — Escape and Conjugation of Zoogametes in Enteromorpha 



compressa Grev. 



Wl 



smaller green algas often entangled with it, I noticed that one of 

 the plants was giving origin to zoogatnetes. I spent some hoars in 

 watching the whole process from the origin of the gametes to 

 conjugation. Although conjugation of zoogametes has h< ea observed 

 in the Chloropln/cea by Areschoug, Derbes and Solier, Tburet and 

 Bornet, Reinke, and others, the following notes may be of some 

 value as being continuous observations on the zoo imetes found in 

 one cell. In the specimen I watched, the actual escape of each of 

 the gametes took from five to fifteen minutes, and the gametes 

 escaped singly. The swarming lasted about two hours, whilst 

 actual conjugation appeared to require certainly over one hour. 

 I was unable to watch the further history of the gametes owing to 

 the lack of daylight. The first stage in the formation of gametes 

 is the aggregation of the chloropliyllaeeous contents to one side 

 (lateral wall/ of the cell. Later tlie contents take up a central 

 position, and have the chlorophyll condensed in the middle, and 

 burrounded by a colourless layer of protoplasm. Division then 

 occurs into eight rounded masses, the young zoogametes. Absorption 

 of the outer end wall of the mother cell (sporangium) then takes 

 place, though this does not happen for some time after division is 

 complete. It would be interesting to know what causes this 

 absorption, and I hope in a future note to refer again to the 

 question. The gametes escape one at a time through the aperture 

 whose diameter is less than that of the gamete, for the latter can 

 be readily seen to be constricted by the edges of the aperture. The 

 green end of the gamete in all cases is first extruded, and a curious 

 Wriggling motion then ensues, lasting from five to fifteen minutes, 

 until at length the gamete frees itself and escapes. The gametes 

 at once assume a pear-shaped form, with a colourless pointed apex, 

 near which are inserted two long and delicate cilia. The pointed 

 end is the anterior one in all subsequent movements. After 

 swarming for from one to two hours, some of the gametes approach 

 each other in pairs. The approximation of two gametes I found 

 did not by any means entail their subsequent conjugation. In 

 many cases I watched two gametes from the mm* cell circle round 

 each other at great speed, and then dash off to renew the process 

 with other gametes from other cells. When fusion actually did 

 take place, the pointed ends coalesced first and then the bodies, 

 and finally the cilia were drawn in. I also selected a favourable 

 specimen which showed signs of gamete formation, and placed it in 

 a glass tube filled with fresh sea-water. One half of the tube 

 I covered with black paper ; the other half was left bare, iatang 

 care to keep the water constantly fresh, and approximately of the 

 same density, I found that after three days the fronds which lay in 

 the exposed part of the tube had formed zoogametes which were 



