122 DR. J. S. BOWERBANK ON SPONGES. [Feb. 13, 



many cases all the four forms occur in different divisions of the same 

 genus; and in some individuals, as in Isodiclya varians (Mon. Brit. 

 Spongiadse, vol. ii. p. 281), as many as three of the primary forms 

 occur mixed in the skeleton ; and in Isodictija iiifundibuliformis 

 (Mon. Biit. Spong. vol. ii. p. 317) we have the spicula of the pri- 

 mary lines of the skeleton attenuato-acuate, while those of the secon- 

 dary lines are acerate, and in many other species we find acerate 

 prevailing in number, but with a considerable admixture of acuate 

 forms, thus totally ignoring the assumptions of Dr. Gray that the 

 forms of the spicula are characteristic of the different families. 

 Neither are " the many-rayed stellate, with rays on all sides, and the 

 three-pronged or three-booked elongate spicules characteristic of the 

 Geodiadee and Tethyadce." Thus the sphero-stellate form occurs 

 abundantly in Bictyocylindrus shiposiis {Mon. Brit. Spongiadse, vol. 

 ii. p. 116) and in many exotic species in no degree allied to either 

 Geodia or Tethea, and ternate or "three-pronged" spicula are an 

 essential part of the structure in some species of Bactylocalyx and 

 other exotic genera. These are not the only crude and inaccurate 

 assertions regarding the general structural characters of the spicula 

 of sponges that are made by the author, but they are sufficient to 

 illustrate the hasty style in which he arrives at his conclusions on 

 these subjects. 



Page 499. Dr. Gray states the object of his proposed new system 

 thus : — "I would propose the following arrangement as bringing to- 

 gether the species which seem most allied, and also as facilitating 

 the study of these very difficult and anomalous animals." The 

 author's generalizations in constructing his system are upon a won- 

 derfully expansive scale. Thus his subclass Porifera silicea, p. 502, 

 will include at least 99 per cent, of the whole number of known 

 sponges, the calcareous ones as compared with the others being ex- 

 ceedingly few in number. 



The first step the author takes in his endeavours to simplify the 

 arrangement of-the sponges is to merge in one subclass the two very 

 distinct divisions of Dr. Grant of Silicea and Keratosa ; and the un- 

 fortunate result is immediately visible in the same and following 

 pages, 503 and 504, in bringing together groups the species ot 

 which are of the most varied and opposite anatomical structure ; 

 and the difficulty is increased by the author's descriptions of his 

 orders immediately following, which are so vague and loosely put 

 together as to be nearly incomprehensible, even to naturalists well 

 acquainted with sponges. 



The first difficulty occurs in his description of section 1, page 502, 

 "J[/a/acospo?'«(Soft-spored Sponges). Reproduction by ova contained 

 in a thin membranaceous ovisac not strengthened by siliceous spi- 

 cules or by gemmules scattered in the substance of the sponge." 

 The author does not seem to be aware that it is comparatively a rare 

 occurrence to find the description of gemmules to which he refers 

 in situ, as they only occur thus at certain periods, and then for only 

 a short time ; so that in thus making them the sole character of his 

 section 1, Malacosporce, he is placing a complete stumblingblock in 



