192 SUMMARY OF CURRENT RESEARCHES RELATING TO 
hurtful external stimuli. The pores of the skin, which always contract 
when the water contains poison, are most sensitive in this direction. 
As a rule, it is not merely the dermal pores that contract under the 
influence of the poisons, but also the superficial canals and chambers. 
Of all animals, Sponges are, physiologically, most similar to plants. 
Sponge-Fauna of Red Sea.* — Dr. C. Keller gives an account of the 
Sponges found in the Red Sea. He commences with the Keratosa, and 
gives a description of the horny skeleton and of the general and minute 
organization of these forms. In discussing systematic questions he gives 
the following table, which will explain itself : — 
Full details as to the characters of these groups are appended. 
The Monactinellidee are next considered, and are divided into the 
two suborders of the Oligosilicina and the Oligoceratina ; the former have 
distinct spongin-fibres, which are either connected together in retiform 
fashion or are arborescent ; monaxial siliceous spicules are inclosed in 
these fibres, and vary in quantity. Free flesh-spicules may also be 
present. In the Oligoceratina the spongin-substance is rare, and there 
are no distinct fibres ; the spicules are connected by spongin or lie 
freely in the mesoderm. The classification given by Messrs. Ridley and 
Dendy in their ‘ Challenger ’ Report is regarded as the most complete 
yet made, although it does not in all respects correspond to the true 
genetic classification. The author again gives a phylogenetic table 
illustrative of his own views, and an account of genera and species. Of 
the latter a number are new. 
Zeilschr. f. Wiss. Zook, xlviii. (1889) pp. 34-405 (6 pis.). 
