1884.] 



MICROSCOPICAL JOURNAL. 



177 



Several months ago — it was in No- 

 vember of last year if we are not mis- 

 taken — Mr. Henry Mills showed us 

 some filamentous extensions from the 

 beautiful discoid diatom, Stephano- 

 discus Niagarce^ found abundantly 

 in the Great Lakes at certain seasons. 

 The filaments were very numerous, 

 and were doubtless quite similiar to 

 those described by Mr. Babcock. 

 They were best seen when the diatoms 

 were mounted dry and illuminated 

 with a paraboloid. They have been 

 observed by Jvlr. Mills for several 

 vears, and he states that they are only 

 found at certain seasons of each year. 

 If the reader will refer to page 8, Vol. 

 Ill, of this Journal, he will find 

 there an account of the appearances 

 described by Mr. Babcock. The sig- 

 nificance of the filaments is vmknown. 

 It may be they are fungoid in their 

 nature, but that seems very doubtful. 

 On page 151 of Vol. i of this Jour- 

 nal will be found an article by J. 

 Brun, entitled ' Parasites on Dia- 

 toms,' in which it would appear the 

 filaments described are mentioned as 

 parasites, and the name Leptothrix 

 rigidula is applied to them. 



Our own observations, made upon 

 the diatoms left by Mr. Mills in our 

 possession, were quite superficial at 

 the time, the specimen being set 

 aside for future careful study. When 

 we attempted to find the filaments at 

 another time they had entirely disap- 

 peared, no preservative having been 

 added to the liquid in the bottle. 

 The subject deserves further study. 

 o 



Photo-micrographs of Bacil- 

 lus. — M. Defrenne recently present- 

 ed some photographic proofs before 

 the Microscopical Society of Belgium, 

 taken from a preparation of Bacil- 

 lus tuberculosis, which were highly 

 spoken of at the meeting. As is well 

 known, it is exceedingly difficult to 

 get reasonably good photographs of 

 this minute organism, and few, if 

 any, have succeeded in making pho- 

 tographs of it that were quite satis- 

 factory. This is due, no doubt, to 



the color of the stains applied. It 

 might be supposed that a red anilin 

 stain would serve the purpose well, 

 but unfortunately it is known that 

 such a color is far from satisfactory, 

 as the light it transmits acts readily 

 upon the sensitized plate. 



The specimens used by M. De- 

 frenne, however, were colored with 

 fuchsin, and in the ordinary process 

 of photographing they failed to yield 

 satisfactory negatives. The idea then 

 occurred to the experimenters to make 

 use of a glass of complementary color 

 to the red stain, placed between the 

 objective and the sensitized plate. 

 The presumption was that the rays 

 forming the image on the sensitized 

 plate would be filtered in passing 

 through green glass, the red rays 

 from the bacilli being if not wholly 

 at least in great part absorbed. Thus 

 the images of the bacilli would be 

 black, while the green light would 

 act upon the plate, and in this way 

 decided contrasts would be obtained. 

 The i-esults verified the expectation, 

 and good photographs were obtained. 



NOTES. 



— Dr. C. S. Dolley, in an interesting 

 communication to the Academy of Natu- 

 ral Sciences of Philadelphia, controverts 

 the statements of Dr. A. Korotnoff concern- 

 ing the presence of a large amoeboid cell 

 in the oesophagus and stomach of Saipa, 

 having the functions of a digestive organ. 

 He says : — 



' Salpa has been very carefully studied 

 by Hermann Fol, who demonstrated, by 

 means of carmine suspended in water, 

 that it threw out a constant stream of mu- 

 cus when excited by the presence of nu- 

 tritive material in the same water, with a 

 reflex action like a salivary gland. The 

 mucus is, by an arrangement of cilia, 

 spread out like a curtain over the inner 

 surface of the branchial sac, when it acts 

 as a means for catching the food partides 

 from the ingurgitated water. By the ac- 

 tion of ciliary bands bordering the groove 

 of the endostyle the mucus is swept to- 

 wards the oesophagus, and as it ap- 

 proaches this it is, by means of the stifi 

 cilia, on the sides of the gill, twisted into 

 a thread and carried, bv a continuation of 



