148 



NATURE 



{Dec. 19, 1889 



to be found, while in Darwinella, triaxon horny spicules 

 abound. 



Very interesting accounts are given of the connective 

 tissue, muscle cells, and nervous system. Stewart's 

 account of the " palpocils " is accepted ; and, although 

 Prof. Stewart's specimens are the only ones which show 

 these organs properly, yet Lendenfeld thinks that, when 

 groups of converging sense-cells are observed (in sections) 

 below the continuous surface, these may be regarded as 

 the cells of a " retracted " palpocil. 



The researches of the author have thrown but little 

 fresh light on the subject of the occurrence of the strange 

 " filaments " in the species of the genus Hircinia ; these 

 filaments are generally more abundant in the superficial 

 layer than in the interior of the sponge. They may be 

 isolated, or arranged in bundles of varying thickness, in 

 which they are parallel. Such bundles are particularly 

 conspicuous in H. gtgatttea, where they form a pretty 

 uniform network which pervades the whole of the sponge. 

 The filaments are never straight : they may be continuously 

 and simply curved, or they are undulating. The latter form 

 of curvature is particularly frequently observed in the 

 filaments which are joined to form large bundles. While 

 their abundance is subject to variation, no case of a 

 sponge with but a few isolated filaments is on record. No 

 apparent young stages of these filaments have been seen. 

 Schulze's researches enabled him to make no positive 

 statement concerning them, but they at the same time 

 demonstrated that "no cellulose is contained in them, 

 that they have no trace of true cellular structure, and 

 that they contain a great deal of nitrogen (9-2 per cent, of 

 their substance), and that they are not Algae. The resist- 

 ance of the filaments in boiling alkali is against their 

 being ordinary Fungi, while their general chemical com- 

 position indicates no relationship to the ordinary sponge 

 skeleton." As to the very minute dumb-bell shaped struc- 

 tures observed by Pol^jaeff, and considered by him to be 

 young stages of the filaments, Lendenfeld thinks that this 

 is extremely doubtful, "particularly as nobody besides 

 Polejaeff has seen them in H. friabilis or any other 

 sponge." But is this so ? for in another paragraph we 

 read : — 



"The spherical bodies which Schmidt and Polejaeff 

 consider as young stages of these filaments— in fact, as 

 terminal knots, either dropped off, or on the way to pro- 

 duce a filament— have also been observed and carefully 

 studied by Schulze, who considers them as monocellular 

 Algae, which have nothing whatever to do with the 

 filaments." 



Lendenfeld says that "no trace of filaments or ' spores ' 

 can be detected in the young embryos which are often 

 found in specimens of Hircinia." 



On the physiology of the group, this monograph throws 

 but little light :— 



" Our knowledge of the vital functions of sponges is at 

 present exceedingly unsatisfactory. We do not even 

 know which parts of the sponge absorb nourishment, 

 or, in fact, what kind of food the sponges take in. We 

 are equally ignorant concerning their respiration and 

 secretion." 



There being then no facts to serve us as guides to 

 knowledge, the next " best thing " is to have recourse to 

 imaginations, and our author " thinks " that " it is by no 



means unlikely that the sponges may exclusively absorb 

 liquid food — that is to say, organic substances dissolved 

 in the water which is continuously passing through their 

 canal system. All the other organisms in which arrange- 

 ments are made to insure a continuous water current — 

 I refer to the higher plants— absorb exclusively nourishing 

 material in solution (the absorption of gaseous food by 

 plants does not concern us here). The existence of a 

 traversing canal system and a continuous water current 

 seems to me to point to the nourishing material of 

 sponges being in solution in the sea-water. The numerous 

 fine sieves and filter arrangements generally, and the mere 

 fact that the water always enters through the smaller holes 

 and is expelled through the larger, clearly shows that the 

 sponges are not desirous that large food-particles should 

 enter their canal system." 



Even granting that the word " exclusively " should be 

 after the word " material," we do not quite understand 

 the comparison of the well-known facts of plant physiology 

 as they are presented to us in the above extract, nor see 

 how it helps us to an understanding of how the sponge 

 adds to its protoplasm ; the undoubted power possessed 

 by some of the sponge-cells to lay down silica, lime, &c., is 

 quite different functionally from the phenomena attending 

 growth and development, using these terms in Herbert 

 Spencer's sense ; but once set a thinking, our author 

 proceeds, and telling us that a " tape-worm is an animal 

 which takes up liquid food, and which has no special 

 digestive apparatus, and that it evidently takes up a great 

 quantity of material from the surrounding chyle through 

 the apparently indifferent cylindrical ectodermal epithe- 

 lium cells ; that the excess material and waste products 

 are got rid of by the nephrydia," he goes on to say 

 that he is inclined " to think that in sponges we may have 

 a similar mode of absorption of nourishment " ; but then, 

 where are the nephrydia or their analogues ? and he 

 thinks again " that it is not impossible that the ciliated 

 chambers may be partly analogous to the nephrydia of 

 the Coelomata, and that the collar-cells may, besides 

 performing other functions, also secrete the urine." 

 However uncertain, he adds, this hypothesis may appear, 

 " I think there can be no doubt that there is more proba- 

 bility in it than in the view, held by Carter and others of 

 the older authors, that the ciliated chambers are merely 

 digestive apparatus." This seems a rather dreamy hypo- 

 thesis, with no facts for its foundation ; but it is but fair 

 to remark that it comes at the very end of a volume which 

 is a record of numerous and important observations. 



Under the headings variability, parasitism, and sym- 

 biosis, many interesting details are given. The author 

 thinks that certain forms of Aulena and Chalinopsilla 

 imitate " certain siliciferous Cornacuspongias. These 

 sponges have descended from thosa which they imitate ; 

 and, whilst they have lost the spicules in the fibres, they 

 have retained the outer appearance of their better pro- 

 tected ancestors in a most striking manner." Apparently, 

 " the primordial sponge ancestors were free-swimming, 

 and had no skeleton. Some produced a calcareous, 

 others a siliceous skeleton ; in both the subsequent 

 development, the formation of ciliated chambers, which 

 the ancestors did not possess, and the fixing of the axis 

 and rays of the spicules, were the same. The primordial 

 Silicea had indifferent irregular spicules, from which the 



