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POPULAR SCIENCE REVIEW. 
attention to the fact that there is nothing written in the 
English language on these worms which will give him any fair 
notion of their structure, or in any way help him to study their 
generic and specific differences. The statements in handbooks 
of zoology are, when correct, too wide and general to be of 
much service, and recourse must be had to the German writings 
of Oscar Schmidt and Max Schultze, and to the French me- 
moirs by Yan Beneden, Claparede, and De Quatrefages. I have 
appended a list of some of these works. The British Museum 
Catalogue of Worms, which professes to give some account of 
the Turbellaria, is most incorrect , and quite useless in relation 
to them. 
The Turbellarians are very soft, flattened animals, very long or 
short, and oval in shape, with their mouths placed ventrally, 
leaving a large prceoral region (prostomium of Annelids).* 
Their internal organs, like those of the other Flat- worms, are 
closely packed together and embedded in their muscular body- 
walls, leaving no free space such as what, in Annelids, is called “ a 
perivisceral cavity ; ” like the other Flat-worms, they never have 
the outline of their bodies broken by the development of lateral 
projecting flaps to be used as feet or paddles ; and like them, 
their growth and development from the egg is complicated by 
very strange metamorphoses, and by the so-called Cf alternation 
of generations.” They agree with them further, though less 
strikingly, in the fact that the yelk which surrounds the egg, 
and on which the young animal is to feed, is in many cases 
secreted by a distinct wide-spreading gland called the 66 vitella - 
rium ; ” and like certain of the Flukes (Trematoda) they have a 
tendency to develope regularly- shaped hard stylets or “thorns” in 
connection with both their prce-oral region (proboscis) and their 
* This prceoral region is an important feature in Turbellarians, and, indeed, 
in most Vermes, forming the •* Kopf-lappen ” or prsestomium in Annelids, 
which may he so elaborately modified into a head with appendages. In 
Turbellaria, the term u prse-ganglionic region ” would he more truthful, since 
the position of the oral opening of the alimentary canal varies, though it is, 
probably, always in the y>o.s£-ganglionic region. I say probably, for certainty 
is very hard to obtain. The proboscis was so long thought to carry the 
mouth, that the true postganglionic aperture has been overlooked ; and this 
may even yet prove to he the case with the genus Acmostomum, observed by 
both Schmarda and Mecznikow. The large-paired ganglia, I believe, in- 
variably mark off an anterior region carrying the eyes, and a posterior carry- 
ing the mouth. This anterior region may he variously modified into an 
expanded frontlet ( Planaria ), or a jointed and spine-hearing proboscis 
( Nemertians , Alaurina, and Prostomium). This view is taken by Professor 
Rolleston, and has much in its favour. But even since writing the above, 
my friend Dr. McIntosh, who is preparing a work on Turbellaria for the 
Ray Society, tells me that everybody is wrong about the mouth in Nemer- 
tians — that the postganglionic orifice exists in a few genera only — and 
hence the above homological views will he upset ! 
