THE STUDY OF DIATOMS. 263 
I shall ever know’! Again, Dr. Dallinger says (respecting 
binary sub-division), ‘this process cannot take place in those 
genera in which axes cross one another like Campylodiscus, 
or in those in which the two valves, although equal, yet constantly 
unite in such a way that the similar parts alternate with one another, 
as may be seen in Asterolampra.’ Once more ‘a slip of the pen’! 
‘the valves of no diatom-frustules, except those developed from the 
sporangial brood, have equal valves, i.e., valves of exactly the same 
dimensions—and every diatom subdivides in the usual fashion, 
whether its axes do or do not cross each other.’ With the remarks 
of the veteran observer, whom we quote, we can but entirely agree ; 
and would refer any one who was curious on these points to such 
memoirs as O. Muller, on Aelosira (Orthosia) arenaria; or Wallich, 
on the relation between the development, reproduction, and markings 
of the Diatomacee. On page 41 the word ‘thallus’ is correctly 
used in its pristine sense, but it is worthy of remark that the term 
‘stipes’ is more usually employed to denote the long or short, 
granular or hyaline, pedicels or branchlets, on which are borne the 
stipitate (not stipate) species : in English books the word thallus 
is usually taken to denote the irregular fibro-mucous masses, 
or branching quasi-fronds, in which many of these forms live em- 
bedded. The notes upon mounting, especially ‘in situ,’ are hardly 
Satisfactory. No varnished cells (asphalt, ‘coachmaker’s-black’, or 
‘black-japan,’) should be used unless they have been gently baked, 
to harden them. To mix benzol with gold-size is superfluous ; but, 
when closing the cell, in wet mounts, both the top of the ring and 
the edge of the cover-glass should be lightly touched with the gold- 
size ; this makes the ‘joint’ doubly secure. An excellent medium — 
- for fuid mounts is distilled water impregnated with a little camphor, 
creosote, or carbolic acid—we agree with Mr. Mills that in water alone 
_ these objects will soon decompose. No mention is made of the 
2 methods of mounting the frustules in Canada-balsam, mono- — 
oe eon, of naphthaline, etc., while the wonderfully concocted _ 
-‘nostrum’ devised by Mr. E. M. Nelson is given #n extenso! _Among 
a matters connected with app 
_ Of Ross & Co. should ‘be omitted ; and among lamps the ‘Bockett- 
lamp’ of Collins surely might have found a place? On objectives . 
one remark is eoubepien aiher viz., that it is not advisable to use — 
_ a higher power than a { in.; this is sound sense, and we advise its 
e consideration by the followers of ‘twenty-fifths and fiftieths ’—as.all 
_ the best work has been performed with comparatively low powers. 
= chapter on Photography will repay perusal by the dilettante 
-opist, #5 home core Tat been bestowed ape se a 
