186 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
forms a quite solid cord, the homogeneous jjrotoplasm of which is not 
rarely filled by a more or less large number of granules ; nuclei may be 
assumed to be present, though they were not seen. The cord is extra- 
ordinarily contractile. It appears to be attached to the sides of the 
hind-gut, at about the end of its anterior third. There does not seem 
to be even a very thin-walled uterus, for the embryos are seen to move 
about in the body-cavity. Shortly before birth the proboscis of the 
embryo appears to be feeling about in all the tegumentary region sur- 
rounding the anus. When it has found the anal cleft it seems to feel 
that there is here no great resistance to its j>ressure, and the embryo 
forcibly breaks through the hindermost part of the cloaca, and reaches 
the exterior through the anus. 
Herr Plate thinks that there are three natural groups of Rotifers, 
which may be arranged thus : — 
I. Digononta; with paired gonads. 
(1) Philodinidae (= Aductifera) ; 
(2) Seisonidae. 
II. Monogononta; gonads unpaired. These may be arranged in 
families on the classification proposed by Messrs. Hudson 
and Gosse. 
Anatomy of Stephanoceros Eichhornii.* — Mr. R. Vallentin remarks 
that, although this Rotifer has been known to exist for nearly one hundred 
and thirty years, much still remains to be learnt concerning its anatomy. 
He has tried to determine some of the disputed points by means of serial 
sections, and states that his results, though good, leave considerable 
room for improvement. 
The tube appears to be formed from mucous cells. There are four 
pairs of muscles, which terminate anteriorly in a sphincter; when a 
living specimen retracts, the bases of the arms are brought together by 
the contraction of this muscle, and the longitudinal muscles being almost 
simultaneously brought into play, the animal retreats rapidly into its 
tube. The “ brain ” is a somewhat cylindrical organ, the walls of which 
are composed of irregularly shaped oval cells; each cell is wholly or 
partially filled with granular protoplasm, and as the secretion present 
in the central space is also granular, it may fairly be assumed that the 
granules originated from the cells and that the cells were in an active 
state at the time of the death of the animal. The protrusile tongue or 
taster, described by Dr. Hudson as connected with this organ, is con- 
sidered to be a duct, while the “ brain ” is a salivary organ. 
The true nervous elements appear to be the large, oval, nucleated 
cells which are placed close to the cuticle on either side of the collar ; 
these have a marked resemblance to unipolar ganglion cells. What are 
generally regarded as eyes are of a chitinous nature and have a central 
opaque mass ; their function is unknown, but it may be safely assumed 
that it is not visual. 
Owing to the large size of the embryos and the comparative small- 
ness of the cloacal opening, Mr. Vallentin thinks that the embryos are 
liberated by the death of the parent. In one series of sections an ovum 
was seen that had formed a gastrula by epiboly. 
* Ann. and Mag. Nat. Hist., vi. (1890) pp. 1-11 (2 pis.). 
