NOTES AND MEMORANDA. 
355 
preliencled as “nine inches.” And, unfortunately, if this be the 
object, the unit is far too largo. Harting saw this difficulty a quarter 
of a century ago, and sought to avoid it by making his unit the 
of a millimetre, which is the one-tenth of Professor Hitchcock’s 
proposed unit. This unit Harting proposed to call the micro-milli- 
metre, and to designate it the letters mmm. were employed. Thus we 
had m. for the metre, mm. for the millimetre, and mmm. for the micro- 
millimetre. But even Harting’s unit was too large, and why Professor 
Hitchcock should have gone back half a century and suggested a 
centi-millimetre, passes our comprehension. 
Such a proposition is, however, open to the fatal objection that it 
introduces a new term which must be unintelligible to all except 
microscopists. For example, an engineer finds a paper in which he is 
interested, and in which the quantities are given in the new unit ; how 
is he to avoid the most serious mistakes unless each paper, no matter 
what its subject may be, shall first give a full explanation of the 
measures used ? The truth is, that this proposition tends to separate 
microscopists from all other scientific men by establishing new and 
unnecessary units, notations, and terms. And the absurdity of such a 
suggestion is at once obvious, when we reflect that all this fuss is 
made merely about the placing of a decimal point, for that is really 
all that it amounts to. The metre and millimetre are well-known 
and universally recognized units, having familiar contracted designa- 
tions m. and mm. To urge the adoption of a new unit is as much a 
backward step as it would be to attempt to revive the old wine and 
beer measures, and bring them into use for special liquids.^ 
Wartelia, a new Genus of Annelida, wrongly considered as the 
Emhrijo of Terebella. — In 1845, in his memoir ‘ On the Development 
of the Annelida,’ Milne-Edwards, after having described and figured 
the transformations of Terebella nebulosa of Montagu, added ; “ I am 
inclined to believe that, from not having known these metamorphoses, 
the larvae of Terebella have been taken for special types, and thus 
genera have been uselessly multiplied.” Since then, the larvae of the 
Annelida have been much studied, and an opposite error has arisen. 
This has happened because instead of following step by step the 
embryo of any given species, from the egg, isolated after its extrusion, as 
was done by Milne-Edwards, some naturalists have employed in their 
researches larvae caught in a fine net, a method which requires the 
greatest care in its application to embryogeny. It is thus that 
Claparede,j' in his ‘ Observations on the Anatomy and Development of 
the Invertebrata,’ J describes and figures, as different stages in the 
evolution of Terebella conchilega, young Annelids, which have in reality 
no genetic relationship with this type, so common on the coasts of the 
English Channel and of the North Sea. 
The observations of Claparede were made at Saint- Vaast-hi- 
* ‘American Journal of Microscopy,’ vol. iii. p. 236. 
t ‘ BeoLachtungcn iiber Anatomic uiul Entwickelungsgcschiclito wiil)clloser 
Tliierc an der Kiiste von Normandie angcstcllt.’ Leipzig, Engelmanu. 1863. 
t Ep. 63-69; pi. viii. ligs. 12 and 13; and pi. ix. 
