422 Bibliographical Notice. 



sponges which are fundamentally different in the nature of their 

 skeleton and in other respects, so that it would be quite impossible 

 to classify them on this principle ? 



The discovery by Prof. C. Stewart of the rudimentary sense- 

 organs or palpocils in sponges is referred to ; but Dr. Lendenfeld 

 claims that he was the first to describe tliese organs in sponges, and 

 that he _has discovered various modifications of a nervous system in 

 horny as well as in calcisponges. An unimportant objection is made 

 to the term " palpocil " for these organs ; but the new one proposed 

 seems hardly necessary. The stratification or layers noticeable in 

 the horny fibres of sponges is attributed to the variable character 

 of the spongin produced by the spongoblasts or fibre-cells at different 

 intervals owing to changes in outer circumstances, and the produc- 

 tion of pith in the fibres of the Hexaceratiua is considered to be due 

 to the action of cells which eat out the fibres and change the spongin 

 into pith ; but this theory has been called in question by Polejaeff, 

 who considers the pith to be an original constituent of the fibres. 



Regarding the physiology of sponges, the somewhat humiliating 

 confession is made that we do not yet know the kind of food which 

 is taken by them, nor how it is absorbed, nor the particular way in 

 Avhich the functions of secretion and respiration are carried on ; and, 

 further, but little is as yet definitely known of the embryology of 

 horny sponges. As to the phylogeny of horny spojiges, the author 

 concludes that they have originated from fotir distinct phyla, which 

 have been developed independently of each other from as many 

 dift'crent groups of siliceous sponges. The system of the horny 

 sponges set forth in this work is stated to be entirely new and fun- 

 damentally different from any previously propounded. The two 

 concluding chapters deal with tlie phylogeny and systematic position 

 of sponges generallj^ and the inevitable ancestral tree is produced 

 — we are told for the first time— showing the relationship of the 

 different famihes of the class. The author considers that the phylo- 

 genetic affinities of sponges are now established on a satisfactory 

 footing, and the merit of this is modestly ascribed to four recent 

 writers of the ' Challenger ' Reports on these organisms and to the 

 author himself. 



Apart from hypothetical subjects, no doubt can be entertained of 

 the value of this Monograph, as giving us for the first time full, 

 detailed, and accurate descriptions of the minute anatomy and other 

 structiiral characters of the group of horny sponges, so that in future 

 there should be no serious difficulty in determining any member of 

 it. Serious exception may be taken, however, to the arbitrary way 

 in which, in many instances, the generic and specific names given 

 by previous authors to many of these sponges have been disregarded 

 and set aside by Dr. Lendenfeld in favour of new terms proposed by 

 himself. It is indeed asserted that the sense in which the terms 

 " variety," " species," and " genus " are used is the result of the 

 authors own original researches and independent of any authority, 

 and further that it is impossible to give a definition of his own 

 peculiar meaning of them ; but such a plea will not excuse the 

 autocratic way in which new names are proposed by which ju'cvious 



