ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
453 
B. INVERTEBRATA. 
Zoological Paradoxes.* — Under this heading Prof. A. Korotneff 
deals with some exceptional forms which “ look like real nonsense, and 
can only as paradoxes excite the interest of naturalists.” 
The first with which he deals is Gastrodes parasiiicum, already 
described as being found in the gelatinous investment of Salpa fusi- 
formis. It is now seen to be an endoparasitic Actinian which has 
become simplified by its mode of life, and so modified as to seem much 
like a Scyphosoma. In its internal cavity there are single and double 
folds, the former consisting only of endoderm, the latter of endoderm 
and ectoderm. These two layers are, in the wall of the body, separated 
from one another by a pretty strong gelatinous layer. The endoderm 
forms six processes which are either true or false septa; the two true 
septa consist of ectoderm also. 
The ectoderm of Gastrodes differs in structure with the age of the 
animal and the part of the body whence it is taken ; thus it may consist, 
on the surface, of one or two layers, while at the floor of the mouth 
there are several layers ; near this it may contain true glands. Eggs 
appear in the ectoderm of quite young forms ; their number, as in all 
parasitic forms, is somewhat considerable ; their presence in the outer 
ectodermic layer is probably caused by their parasitic habit. The 
author has been able to detect what appear to be spermatozoa. 
The endoderm seems to have a very peculiar construction ; it con- 
sists of small cylindrical cells found at various spots on the inner wall 
of the stomach ; these cells form the base of the gastric lumen which 
seems to be very much reduced, as it is almost completely filled by 
various endodermal elements ; the endoderm of the gastric tube spreads 
out into a layer which lines the inner side of the oral disc and serves as 
the seat of origin of the spermatozoa. These cylindrical cells pass into 
others which form the peculiar endodermal mass ; this consists of large 
vesicular elements, rich in yolk. There are other cells which are still 
more remarkable ; here and there, and ordinarily inclosed in the endo- 
dermal mass, there are aggregations of protoplasm of a finely granular 
substance. No cell-boundaries are to be detected here. This plasmo- 
dium perhaps serves to effect chemical changes in the food. 
The nearest ally of Gastrodes would appear to be Scyphosoma. 
The next form discussed is also one on which Prof. Korotneff has 
before written ; it is the remarkable creature called by Metschnikoflf 
Cunoctantha parasitica. A number of stages have now been observed, 
and it would seem that the ectoderm always consists of seven cells which 
exhibit absolutely no tendency to increase. In the endoderm it is other- 
wise. In Cunoctantha there appears to be a case of sporogony. 
The author states he has but little to add to the careful descriptions 
already given by R. Hertwig and Fol of the structure of the rhizopodal 
Sticholonche zanclea. The pseudopodia resemble exactly the proto- 
plasm of the Heliozoa, for an axial homogeneous portion and a finely 
granular protoplasmic investment are to be seen. The relation of 
the pseudopodia to the body-mass appears to be also the same as in the 
* Zeitschr. f. Wiss, Zool., li. (1891) pp. G13-28 (3 pis.). 
