128 



HARDWICKE'S SCIENCE -GOSSIP. 



tion of indigo along the median line, and its penetra- 

 tion into the interior of the diatom, particularly in 

 Stauroneis kept for some days in indigo water. 

 Beside this demonstration, I was able, by the em- 

 ployment of the pigment, to obtain a glimpse of the 

 mode of progression in the large Pinnularias. I am 

 half tempted to send you my drawings. Many cases 

 of conjugation are not always so simple as is generally 

 supposed. 



" When a large Pinnularia is observed in the field 

 quite blue with indigo, we see in side-view (fig. 90) 

 little particles of indigo running along the (X) raphe 

 as far as the end of the median line ; here they accu- 

 mulate into a little ball, at C. In fig. 90, (7 b, 

 a little ball is seen on each side, but that which is 

 most surprising is, these balls revolve on their axes. 

 When the ball acquires a little size it suddenly breaks, 

 and the particles sail off in the direction a e (fig. 91), 

 and a new ball is again formed ; this is on supposition 



d < — 



a 



• -- 



^""V 



Fig. 90. Side view of Pinnularia, showing balls of Indigo 

 running alongside. 



-O •^>*SMS^a3BB83!D) |f i| d 



Fig. 91. Diatom, showing mode in which ball of Indigo breaks. 



Fig. 92. Diatom in act of Deduplication at a and b. 



that the frustule is moving in the direction of the 

 arrow d. Moving the other way, the particles slip 

 down the other half of the median line or raphe, and 

 form a little ball, as before, at its end. I have 

 watched this for hours, and I can assure you that it is 

 a glorious sight. I had some magnificent large Pin- 

 nularias, and these effects were best seen when the 

 motion forward of the frustule was prevented by its 

 coming in contact with some particle of sand or dust. 

 The colour in the field was the ordinary indigo-blue 

 water colour, pretty thick. Furthermore, there 

 always appeared a gelatinous envelope which pre- 

 vented the actual contact of the indigo particles with 

 the frustule, which, as it moved forward, pushed them 

 in advance, as at d (fig. 90). The slightest applica- 

 tion of aniline red (Fuchsine) demonstrates the 



external gelatinous covering by the absorption of the 

 colour, even before the colour is seen elsewhere in the 

 field, but this aniline instantly arrests all motion of 

 the diatom. 



" The act of deduplication of the primordial utricle 

 is effected with great rapidity; it manifestly commences 

 at the two ends of the frustule at the points a and b 

 (fig. 92) ; the membrane there forms a fold, which is 

 gradually prolonged until it reaches the central 

 nucleolar mass ; this occupies about six minutes from 

 the commencement of the phenomenon. 



" I have never been able to perceive a true circular 

 nucleus in Pinnularia major (Ehr. ), but it is very 

 visible in divers species of navicula, such as N. firma, 

 and in the Stauroneis. It is very manifest in the 

 Surirellas. The frustules only separate from each 

 other in seven days, rarely before. The conjugation 

 in the Pinnularias continues for four days before the 

 act is entirely completed. I have followed it step by 

 step, and measured with a micrometer the sporangial 

 development. ... I remain, &c, 



"H. L. Smith." 

 (The above experiments are of great interest, and 

 will, I hope, be repeated by other diatomists. 

 The study of the living frustule has, I fear, been too 

 much neglected for that of the dead valve, the 

 diatomist having been seduced by the elegance of its 

 contour and the beauty of its ornamentation. If, as 

 Professor Smith describes, the communication with 

 the interior of the frustule is through minute apertures 

 at the termination of the raphe or median line, it is 

 evident that those forms which do not possess this line, 

 and are neither alate nor carinate, must possess some 

 other means of communication ; in the Aulacodisci 

 this may be by means of the processes which are 

 apparently perforate, but in the Triceratia, Coscino- 

 disci, &c, I think M. Deby's suggestion, that it takes 

 place at the margins of the connectives, is probably 

 correct. — F. K.) 



Those interested in the structure of the diatom frus- 

 tule will find much valuable information in the papers 

 of Dr. Wallich, particularly that published in the 

 Monthly Mic. Jour., Feb. I, 1877. A paper by the 

 same author, entitled " Are the Desmids and Dia- 

 toms simple Cells?" will be found in the April part 

 of Popular Science Rci'ieiv, 1877. 



A GLASS-EATING LICHEN. 



ON visiting an antiquarian friend, to whom I am 

 indebted for the loan of specimens, &c, some 

 old stained glass of about the fifteenth century was 

 submitted to me, and an opinion asked as to the cause 

 of certain irregular worm-eaten-looking holes of some 

 depth, occurring generally only over one surface of the 

 plates. My friend informed me that it was publicly 

 discussed some twenty years ago as to its cause, for it 

 had often been observed in old glass windows. At 



