SCIENCE- GOSSIP. 



28: 



free, single, disc-shaped, valves circular, il.it 

 or slightly convex, exhibiting a cellular or 

 areolar appearance, no internal septa nor late- 

 ral processes ; marine and fossil. Tei'psinoe 

 nmsica (fig. 6) : frustules faintly punctate, front 

 view rectangular oblong, side view equally inflated 

 in middle and at the ends, nodules separated by 

 septa ; found in saltwater only. Arachnoidisciis 

 ehreribergii (fig. 7) : frustules adherent, disc-shaped, 

 valves plain or slightly convex with radiating and 

 concentric lines (rows of dots) and a central pseudo- 

 nodule ; marine only. Trinaeria regi/na (fig. 8) : 

 frustules with three broad bispined. equal-lengthed 

 processes, margin pearly, angles naked ; marine 

 only. Heliopelta leeuwerihoeckii (fig. 9) : frustules 

 single, valves circular with imperfect radiating 

 septa, markings absent in centre, but as many 

 large submarginal apertures present as there are 

 rays, and numerous erect opposite submarginal 

 spines on each side ; the spines connect the pairs 

 of young frustules; fossil. Actinorychts elureribergi i 

 (fig. 10) : frustules free, single, or disc-shaped, 

 valves circular, exhibiting cellular markings with 

 rays or bands radiating from centre, which is free 

 from cellular appearance, no internal septa : fossil. 

 A.ctinoptychus sena/rius (fig. 11): frustules free, 

 single, or disc-shaped, with six rays and internal 

 radiating septa, valves apparently cellular except 

 opposite the rays ; fossil. Aulacodiscus kittonii 

 (fig. 12) : frustules single, disc-shaped, circular, 

 without internal septa, valves furnished with 

 tubular or spiniform processes ; marine and fossil. 



Remarks. — This series of slides contains a very 

 perfect example of Istlvmia enervis. I never saw 

 the secondary markings more clearly. On ex- 



photograph this appearance, and regret I have not 

 time to try. I insert a photo of Tgthmia nervosa 

 (fig. 13) which I made some time afro with a 

 •jj oil-immersion lens. This shows distinctly the 

 secondary areolations surrounding the primary 

 ones, as maybe seen in Tgthmia mentis; but the 

 perforations in the centre of the primary areola- 

 tions were not very visible in this specimen, and 

 are not reproduced in the photo. Aulacodiscus 

 kittonii should also show interesting secondarv 

 structure.— J". It. L. Dixon, MIL C.S.. /,. Tt. < '. /'. 



[Those of our readers who require further in- 

 formation on the preparation of diatoms are referred 

 to a couple of articles by Mr. Edward H. Robertson 



11 



/ z 



A l±l a <° oil 3 1 



S"assil 



T fL? 



Diatom-. 



in Science-Gossip, vol. v., N.S., pp. 172-174 and 

 211-212. In vol. hi., pp. 32-31, appeared an article 

 by the Rev. Adam Clarke Smith on the " Generic 

 Names of Diatoms," which will be found useful to 



7 





*?~ 



amination with an oil-immersion lens, the primary 

 areolations are seen to be surrounded by small 

 secondary areolations, and in one specimen, on the 

 valve surface particularly, the centre of the primary 

 areolations maybe distinctly seen to be perforated. 

 I do not know whether it" would be possible to. 









« * * \ c ■ i . ' • * • 

 •— * " - - ^ « '> ' « ' ..^^ 



Fio. 13. Isthmia nervosa. 



those who are not familiar with the nomenclature. 

 The figures illustrating these notes, except fig. 13, 

 are by Miss Florence Phillips, the hon. secretary 

 of the P. M.S., and are drawn from the original 

 slides which accompanied the notes. We have 

 reprinted the latter in the hope that some of our 

 readers may be induced, by the simplicity of the 

 methods given, to take up the study of diatoms 

 perhaps the most fascinating of all microscopic 

 studies — and we have for this reason abstained 

 from further elaborating them. Dr. Carpenter, in 

 " The Microscope and its Revelations *' (seventh 

 edition), devotes many pages to the subject, and 

 to these we may refer the reader. — Ed. Microscopy, 

 S.-G.] 



