86 Development of the Ovum. By IV. H. Dallinyer & J. Dnjsdale. 
to me that there had been actual vesication, and that steam, 
formed in the scale, had raised a very delicate membrane, carrying 
up with it the plumules from the substance of the scale, much as 
a piece of blistered cuticle carries up fine hairs from the cutis off 
which it is raised. The “lined and beaded appearance” is produced 
by the running together of the images of the plumules when the 
glass is imperfectly focussed, or the light is badly thrown. The 
plumules only come out when they are softly illuminated all round 
and appear as if lighted from above, and when only a very slight 
glare is allowed to show at one part of the field, i. e. just beyond 
the free end of the scale. Under the same glasses, by ordinary 
central-light illumination with Powell and Lealand’s new condenser, 
the substance of this scale is transparent, and the featherlets appear 
rounded out into fine “ exclamation notes,” as shown in Mr. Beck’s 
well-known drawing and in Colonel Woodward’s photograph. 
Careful measurement of some large detached featherlets by 
means of Powell and Lealand’s beautiful cobweb micrometer showed 
them to be about a hich in length and ^ruinr inch in breadth. 
IV . — The Development of the Ovum. 
By W. II. Dallinger, V.P.R.M.S., and J. Drysdale, M.D.* 
Few subjects can be more important in their bearing on biology 
than the more prominent of those considered in this volume, it 
now rests on a morphological basis which will never be shaken, 
that there has been a procession of the most complex animal forms 
from simpler and still simpler ones, until we reach eventually the 
ultimate of organized simplicity. There may be difficulties in the 
way, but they are as nothing to the overwhelming evidence which 
morphology provides in its support ; doubt, indeed, is no longer 
possible ; and every year diminishes the circumscribed area of diffi- 
culty. But our knowledge hitherto of the developmental processes 
which take place in the earlier states of the simplest elementary 
organisms is wholly incompetent. Much labour has been expended, 
and doubtless good work has been done ; but as it at present stands, 
it is conflicting, crude, and essentially wanting in coincidence and 
correlation. The work t before us is the result of an attempt on 
* This paper appeared as a review in ‘ Nature,’ July 5 and 12. It seems 
worthy of a place in our pages as an original contribution to a certain extent. 
t ‘Biitschli on the Earliest Developmental Processes of the Ovum, and on 
the Conjugation of Infusoria.’ (‘Studien iiber die ersten Entwicklungsvorgiinge 
der Eizelle, die Zelltheilung uud die Conjugation der Infusorien.’ Von O. 
Biitschli. Frankfurt, 187C.) 
