THE AMEEICAN MONTHLY 



[January, 



from the cut, the slide-box proper is 

 held in an outer case, which not only 

 affords additional strengtli, but also 

 effectually excludes dust. 



An Inftisorian in the Water of San 

 Francisco. 



BY A. H. BRECKENFELD. 



A beautiful and exceedingly inter- 

 esting infusorian is to be found at 

 present in the water supply of this 

 city in such immense numbers as to 

 entitle it to a more than ordinary share 

 of attention and study. It has re- 

 cently been brieffy described by Dr. 

 Hopkins, a microscopist of this city, 

 bvit I think the gentleman has fallen 

 into a quite natural error in regard to it. 

 He regards it as a vegetable organism, 

 and has classed it with the Diatoma- 

 cese, considering it a species of Syr- 

 ingldium (Ehr.), which is, by the 

 way, a marine genus, with no fresh- 

 water species. The appearance of 

 the form in question would very eas- 

 ily lead an observer to consider it a 

 diatom, for its rigid lorica is hard and 

 flinty looking, and its markings strong- 

 ly resemble those of certain diatoms — 

 for instance, those of the genus Isth- 

 mia. Then, too, the slow and hesi- 

 tating movement of some of the living 

 individuals is often very much like 

 that of the free diatoms. The Dia- 

 tomacccB, however, without excep- 

 tion, secrete a siliceous shell or epi- 

 derm (this being in fact one of the 

 principal characteristics of the group) , 

 and either subjection to a white heat, 

 or boiling in nitric acid will merely 

 dissolve the contained endochroine, 

 leaving the frustule itself clean and 

 entii^ely uninjured. But on applying 

 these tests to the form alluded to it is 

 completely destroyed, and with it its 

 claim to be considered a diatom. It 

 will have to be referred, I think, to 

 the genus Ceratium (Shrank.) be- 

 longing to the order Peridinina of the 

 Cilio-flagellate Infusoria, and is very 

 probably Ceratium longicorne. 



A sketch of this particular species 



can be seen in No. 3 of the " Portfo- 

 lio of Drawings," published by T. 

 Bolton, England, and agrees almost 

 perfectly with the appearance of the 

 Ceratium found in " Spring Valley," 

 but shows a flagellum between two of 

 the shorter spines. Carpenter in his 

 work, "The Microscope," also gives 

 an engraving of two other species of 

 Ceratium each showing a flagellum. 

 I must confess that, although using 

 an excellent Spencer one-quarter-inch 

 objective (dry) of 115° angle, and a 

 C ocular, I have not yet been able to 

 demonstrate the existence of either a 

 flagellum or of cilia. In attempting 

 to render them visible I have tried 

 the effect of both tannic and osmic 

 acids, and also of other reagents and 

 staining fluids, but thus far without 

 success. This may, perhaps, be ac- 

 counted for by the theory that these 

 creatures may now have passed into 

 the "still" condition, and the rapid- 

 ity with which they subside to the 

 bottom of the water containing them 

 — forming a dense layer there — lends 

 some plausibility, I think, to this view. 

 The characteristics of the genus are : 

 "Body with transverse groove, the 

 two portions of the facetted lorica 

 nearly equal. Carapace has horn- 

 like processes." This description ap- 

 plies perfectly to the infusorian under 

 consideration. The micrometer shows 

 its average length to be about .0085 

 inch and its width .0035 inch. The 

 horn-like processes are slightly ser- 

 rated, or spinous, the three shorter 

 ones on one hemisphere being shai'ply 

 pointed, while the long one project- 

 ing from the other is blunt at the end. 

 They have no joints, are perfectly 

 rigid, and the entire lorica has a glassy 

 appearance, and, when properly illu- 

 minated, sparkles as brilliantly as a 

 polycystine. From the equatorial 

 groove to the base of one of the three 

 spines is quite a deep depression 

 (best seen in an empty carapace) , into 

 ^vhich several European observers of 

 this form have seen the flagellum sud- 

 denly withdrawn. This depression 

 has been conjectured to be a true 



