^^*j8.] dr. j. s. bowerbank on sponges. 121 



of the whole of the immerous vague and extraordinary alterations in 

 the existing systematic arrangements of the Spongiaclte proposed by 

 him with a degree of hasty inconsideration that has led him into 

 errors of omission and commission too numerous to be mentioned in 

 detail ; I will not, therefore, attempt a minute critical examination of 

 his new system of arrangement, but content myself with pointing out 

 the prominent errors and inconsistencies of his plan. Thus, in page 

 493, he writes: — "The division between the calcareous and siliceous 

 sponges is very distinct and natural; the separation between the 

 siliceous and keratose sponges, on the other hand, is very indistinct 

 and separates nearly allied genera." But he does not state what are 

 the nature of these alliances ; nor does he seem to consider that the 

 alliance must really be closer between sponges having spicula with 

 calcareous or siliceous bases than between either and those having 

 no spicula at all. And he then enumerates a series of distinctive 

 characters belonging to the Spongiadae that are, upon the showing of 

 his own descriptions of them, amply sufficient to establish each as a 

 separate order or genus ; and having done this, he concludes the 

 paragraph thus :— " I believe it better to unite the siliceous and 

 keratose sponges of these zoologists into one group or order." He 

 then discusses the skeleton-spicula in the same loose manner, thus: — 

 " The spicula that form the main part of the skeleton of these sili- 

 ceous sponges are of three shapes : — 



" Fusiform (acerate, Bowerb.), more or less cylindrical, and pointed 

 at each end. Needle-shaped (acuate, Bowerb.), cylindrical, blunt at 

 one and sharp at the other end. Pin-shaped (spinulate, Bowerb.), 



cylindrical, with a more or less spherical head and a tapering point," 



totally omitting to mention the true cyhndtical form, plate 1. fig. 12, 

 ' Monograph of British Sponges,' and "entirely ignoring the first three 

 primary forms of acerate, acuate, and spinulate, neither of which are 

 fusiform in their typical forms, the fusiformity and the attenuation 

 being merely secondary characters, or variations of the typical forms, 

 and applicable ahke to the whole four of them. 



The author then describes the whole of the auxiliary spicula of 

 sponges in the same loose and hasty style. He writes—" The stel- 

 late are usually scattered in the sarcode ; and the three-pronged are 

 what Dr. Bowerbank calls tension and defensive spicula." This 

 IS quite incorrect as regards the "three-pronged" spicula, as I 

 have never designated them as tension spicula, but always as de- 

 fensive ones. He then proceeds thus— "The forms of the spicules 

 are characteristic of the different families, if they are not always 

 peculiar to them. Thus the many-rayed stellate, with rays on all 

 sides, and the three-pronged or three-hooked elongate spicules are 

 characteristic of the Geodiada and TethyadcB. The anchorate and 

 birotulate spicules and other forms of the series are almost peculiar 

 to the family Esperiadw" These assumptions of Dr. Gray are also, 

 to a great extent, erroneous. In the first place, I totally deny that 

 "the forms of the spicules are characteristic of the different families." 

 On the contrary, the primary skeleton forms are common to all of 

 them ; the spicula are not characteristic even to a genus ; and in 



