1892.] MICROSCOPICAL JOURNAL. 271 



Very soon he was deluged with inquiries as to where the deposit 

 was located, and re([uests for more of the material. The frag- 

 ment having been picked up on the beach below Santa Monica, 

 where it had been left at high tide, and there being no ledge or 

 stratum from which it might have been broken, Mr. Ashburner 

 was unable either to send quantities of the material or locate the 

 deposit. 



Briefly stated, the Santa Monica deposit is famous for its pecu- 

 liar combination of species of diatoms, for the large number it con- 

 tained (Mr.H^de had slides on exhibition containing iSi difterent 

 species), for the rarity of many of these species, and for their 

 wonderful beauty and brilliancy. No other deposit has yet been 

 discovered which equals it. 



In 1S7S Mr. Ashburner received a letter from Charles Stoddard, 

 of Boston, regarding the peculiarities of this Santa Monica deposit. 

 It was I'emarkable, he said, for its great resemblance to the noted 

 Barbadoes deposit. It contained numbers of rare forms, which 

 were first published by Greville as occurring in the Barbadoes 

 deposit, and one rare form found by this author in Moron, Spain ; 

 one by Ehrenberg as occurring only in Greece, and three species 

 of Dr. William Gregory's diatoms of the river Clyde. Thus were 

 brought together in one deposit species originally found in local- 

 ities widely separated, both in time and space, without noticing 

 the numerous common forms so universally distributed about the 

 globe. 



In most orders in nature, the speaker said, both in plant and 

 animal life, there is usually a wide range of individual variation. 



One result of this is that if carefully arranged in a certain series, 

 one end of the series would show a close resemblance to an order 

 quite distinct ; while at the other end of the series there would 

 be observed a like resemblance of its concluding forms to another 

 and distinct order, so separated from it that the two could never 

 for a moment be classed together. Not only is this observable in 

 the larger orders of the animal and vegetable kingdoms, but it is 

 equally so in orders within orders, sub-genera within genera, and 

 even among species ; until there would seem to be, from any 

 point in the series, an ascending and descending scale of allied 

 forms that to the mind not deeply scientific would defy classifica- 

 tion. So in the diatoms, although undoubtedly vegetable, they 

 are absolutely separated from their relations, the desmids, by the 

 fact of then- silicious envelope or outside skeleton, which is 

 entirely wanting in the desmids. Yet certain forms in the two 

 orders resemble each other far more closely than certain genera 

 of each resemble other genera of its own order : for example, 

 Closterium among desmids and Epithemia among diatoms ; Des- 

 midian among desmids and Fragillariae among diatoms. Thus 

 with a series of gradual changes from the forms just named, pass- 

 ing by slight gradations from one genera of the diatomace^e to 

 another, looking at isolated examples, it is difficult to believe they 



