572 SUMMARY OF CURRENT RESEARCHES RELATING TO 
in Clavelina, muscular elements which are of the type of the primitive 
bundles of Vertebrates, and yet are of mesenchymatous and not epi- 
thelial origin. Whether it was necessary to put another nail into the 
coffin of the Hertwigs’ theory is another question. 
Development and Formation of Excretory Canals in Cercaria 
echinata.* — M. J. Chatin has studied these canals in the larva of 
Distomum echinatum, which dwells in aquatic Molluscs. The first sign 
of a future canaliculus is a small band of small cells, with relatively 
large nuclei. Soon the cells seem to fuse, their boundaries disappear, 
and a kind of plasmodium results ; this exhibits great activity, as is 
shown by nuclear proliferation ; the number of nuclei increases, and 
indicates the beginning of the third period which corresponds to the 
appearance of the canal proper. In a section parallel to the long axis 
of the plasmodial band a conical space is seen, while in a section at 
right angles to this there is seen a narrow cavity with sinuous edges. 
These observations show that the views generally accepted do not 
hold universally ; the formation of excretory canals is not always brought 
about by the perforation of a column of cells ; nuclear proliferation 
plays an important part, and, with protoplasmic activity, succeeds in 
realising organic conditions which are necessary for the working of the 
apparatus. 
Anatomy of Taeniidse.f — Herr M. Liihe has been investigating the 
structure of the rostellum and the musculature of the scolex of the 
Tmniidee, and gives a preliminary account of his results. The lately 
established subfamilies of the group appear to have a characteristic type 
of structure. With regard to the rostellum of the Cystotaeniidas little 
can be added to the statements of Nitsche and Leuckart ; the cells seen 
by the former in the bulb of T. crassicollis are ganglionic. 
The rostellum of the Cystoidotaeniinae consists of two muscular sacs 
with an internal circular and an external longitudinal layer of muscles, 
though the latter may be wanting; in Dipylidium and some avian 
Taeniae the whole outer sac is absent. The rostellum of the Davaineidae 
is an oviform or lenticular body w T hich essentially consists of longitudinal 
muscles imbedded in a layer of connective-tissue. Taeniae of Fishes 
sometimes, at any rate, have merely a rudimentary lenticular rostellum. 
Intermediate stages between these types have not been found as yet. 
The author has seen nothing which leads him to suppose that the 
rostellum ought to be considered as a modified rudiment of the enteron, 
but the test of developmental history has not yet been applied to the 
question. The axial muscular cone of the Anoplocephalinae consists of 
stellate crossing fibres which serve to withdraw the suckers from the 
pits at the base of which they lie when in a condition of rest, and to 
flatten them out at the same time ; these are best developed in Anoplo- 
cephala perfoliata and A. decrescens. Mesocestoides litterata has muscular 
fibres in the scolex which similarly connect the suckers with one another. 
The muscular cones give as little support as the rostellum to the view 
that they are the remains of a pharyngeal musculature ; they would 
* Comptes Rendus, cxviii. (1894) pp. 1356-8. 
f Zool. Anzeig., xvii. (1894) pp. 279-82. 
