T. H. BUFPHAM ON CONJUGATION OF ORTHONEIS BINOTATA. 29 



applied to the upper side of the upper sporangial frustule, and 

 the other valve to the lower side of the lower frustule. The 

 old lower frustule — which, perhaps, we must not call the male 

 — is usually seen as two clean valves slightly separated and 

 lying nearly vertically to its old position (Fig. 11). Now in this 

 case the original perigloea, although deformed, remains at the 

 base of the sporangium, and the tentaculoids can still be seen. 



The process of conjugation just described would fall under 

 Smith's I. class (Brit. Diatoiyiacecc, Yol. ii, Introd., p. xii) in 

 which " we have two parent frustules and two sporangia [i.e., 

 sporangial frustules] as the result of their conjugation." 



The new valves are exactly like the normal ones in siliceous 

 firmness and in other characteristics. As they are 46 jj, long, 

 and vegetative frustules have been measured to 42 /x in length, 

 there is no doubt that the sporangial frustules issue from the 

 sporangium (which may be seen empty and deformed) and 

 assume a perigloea and multiply in the way normal to diatoms. 



This diatom seems to have only one British record, and that 

 is only of the valve. Roper published this in 1858 as Gocconeis 

 scutellum Ehr., var. y (Quarterly Journ. of Microscopical Science, 

 Vol. vi, 1858, p. 24, PI. iii, Fig. 9). He found this in one 

 gathering at Lyme Regis, and it is clear that he had not ob- 

 served the frustules in situ. In 1863 Grunow regarded it as a 

 distinct species and it became G. hinotata, Roper's valve being 

 var. stauroneiformis. (Verhandlungen der zoologisch-botanischen 

 Gesellschaft in Wien, Band xiii, p. 145, Tab. iv, Figs. 13, 14). 

 The same author in 1877 describes the valve as differing from 

 Gocconeis, and says " two long horns (in the living frustule) 

 project from it at the places where the semi-circular plates are 

 situated," and he regards these "horns" as distinguishing 

 Orthoneis from Mastogloia (Monthly Microscojoical Jouryi., Vol. 

 xviii, p. 177). The mode of conjugation described now would 

 certainly distinguish it from Gocconeis. Smith places the last 

 named genus in his III. class where a single frustule produces 

 a single sporangium [=sporangial frustule], (Loc. cit. p. xii, 

 PI. B.) 



It seems clear then that the plates have some physiological 

 value. Whether the tentaculoids are of any assistance to the 

 organism in its " struggle for existence " is not evident to me, 

 and I have no suggestion of any value to make. 



