110 ZYGOPHYCE.E. 



narrower, and perfectly elliptical, with abrupt ends. How the spores 

 behave when germinating I have not yet had any opportunity of observ- 



" Thus it appears from the foregoing details that the spores are always 

 formed without a preceding act of conjugation. The spore formation, 

 therefore, may be regarded as neutral, or we may assume that as in 

 exceptional cases spores may be formed by the instrumentality of a 

 single cell, in this ease the exception has become the rule, and the spores 

 would then be regarded as parthenospores, and not as agamospores." 



Under these circumstances of development, Wittrock considers him- 

 self justified in proposing the genus Gonatonema for the two forms, the 

 one Gonatonema ventricosum, on which the above observations were 

 made, and the other the species which Hassall described as Mesocarpus 

 notabilis. 



Gonatonema notabile. (Hass.) fVittr. 



Sterile cells 8 to 10 times as long as broad, sometimes longer. 



Zygospore, front view cylindrical, side view bent so as to be 

 convex on one side, concave on the other, truncate at the ends^ 

 same diameter as the vegetative cells. 



SIZE. Cells -012--015 mm. 



Wittrock Mesocarpea3, p. 16, fig. 14. 

 Mosocarpus notabilis, Hass. Alg. 170, t. 46, f. 2. 

 Mougeotia notabilis, Hass. Ann. Nat. Hist. x. p. 46. 

 Staurospermum notabile, Rabh. Alg. Ear. iii. 261. 



Found in great abundance in some brick fields near Netting 

 Hill. Hassall. 



Here follows the original description by Hassall : " Filaments at first 

 cylindrical, but subsequently becoming angulated, the angle of flexion 

 being situate in the centre of each cell. Cells usually about 8 or 10 

 times as long as broad, but frequently longer. Sporangia non-symme- 

 trical, a single one being placed in the angle formed in each of the cells." 



We have nothing to add to this description, never having seen the 

 plant in question, and are able only to reproduce Hassall's figures. 



Plate XL1 V. fig. 3. a, sterile cells ; b, fertile cells, after Hassall. 



