748 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
two most probable phylogenetic views, those of Neumayr and the 
Sarasins. 
Ludwig’s Echinodermata.* * * § — Prof. H. Ludwig has continued the 
publication of his valuable treatise. The parts before us commence 
with a postcript, in which some recent discoveries in Holothurians are 
reported, which bear on the already concluded chapter on Morphology. 
The history of development is next dealt with in considerable detail, and 
the author then passes to the systematic arrangement of the Holothuri- 
oidea, which he divides, primarily, into the two groups he has lately 
established, the Actinopoda and the Paractinopoda.f The various 
divisions as low as genera are defined ; for the species the student is 
referred to Thiel’s excellent ‘ Challenger ’ report. The parts to hand 
conclude with an account of the geographical distribution of the class, 
which is illustrated by a series of small maps. 
Apical System of Echinoids4 — MM. C. Janet and L. Cuenot have 
some observations on the terminology of the apical apparatus. They 
are of opinion that the plates ordinarily known as the oculars should be 
called terminals. They also call attention to some examples of multiple 
genital orifices, which they consider to be of a teratological nature, and 
not a return to the condition which obtains in the Palseechinoids. As it 
is merely a question of absorption of calcareous matter, this may happen 
at two or three adjacent points instead of at one only. In some cases 
the madreporic pores extend beyond the area of the madreporite, and 
they describe an example of Arbacia punctulata in which they have 
observed it. 
Coelenterata. 
Histological Observations on Ccelenterata.§ — Dr. K. C. Schneider 
has found that by the aid of the Hertwigs’ osmium and acetic acid 
mixture it is possible to discover ganglionic cells on the tentacles and 
the pneumatophore of Apolemia uvaria and on the polyps of Forskalea 
contorta ; these do not essentially differ from the ganglionic cells 
found in other Coelenterata. Sensory cells of the usual kind have 
been found at the anterior end of the polyps and tentacles of Apolemia. 
In the stem of this form and of Yelella spirans , very remarkable and 
abnormal cells have been detected ; the epithelium consists of cells of 
very various forms, between which intermediate stages may be made 
out. In Forskalea there are at the sides of the trunk transversely 
elongated cells which send a process inwards ; with this, which may 
divide, the longitudinal muscles become connected. In a young 
Halistemma , in the trunk of which the central canal is extraordinarily 
wide and the septal elevations of the supporting lamella very low, their 
relations were particularly well seen ; from which it follows that we 
have here to do with epithelio-muscular cells. Circular muscular fibres 
do not appear to be present. In Apolemia , however, muscular substance 
is inclosed in these prolongations of the cell-body, as also in the 
central processes which lead to the longitudinal muscle ; at the same 
* Bronn’s Klassen u. Ordnungen des Thier-reichs. II. 3, Echinodermen, 1891 , 
pp. 241-376 (pis. xiii.-xvii.). f See this Journal, ante , p. 478. 
% Bull. Soc. Geol. France, xix. (1891) pp. 295-304 (11 figs.). 
§ Zool. Anzeig., xiv. (1891) pp. 370-1 ; 378-81. 
