NOTES AND MEMOKANDA. 177 



by Professor Schulzo, and tliat, " considering the diflficulties of obser- 

 vation, it appears better to assume for tliis and some other descriptions 

 that the observations are in error rather than that there is a funda- 

 mental want of uniformity in development amongst the Spongida." 

 It would be superfluous for us to lay stress on the value of Mr. 

 Balfoui-'s opinion on such a matter as this. 



Morphology and Systematic Position of the Spongida. —In an 

 article in the ' Quarterly Journal of Microscopical Science,' * Mr. 

 Balfour points out that Schultze's last memoir f on the development 

 of Calcareous Sponges confirms and enlarges Metschnikoff's earlier 

 observations, | and gives us at last a fairly complete history of the 

 development of one form of calcareous sponge ; and the facts thus 

 established have suggested to him a view of the morphology and 

 systematic position of the Spongida somewhat different to that now 

 usually entertained, though it does not claim to be more than a mere 

 suggestion, which, if it serves no other function, may perhaps be of 

 use in stimulating research. 



After a brief statement of the facts which may be considered as 

 established with reference to the development of Sycandra rapJianus, 

 the form which was studied by both Metschnikoff and Schulze, 

 Mr. Balfour says that he thinks that the larva represents an ancestral 

 type of the Spongida, consisting of a colony of Protozoa, one-half 

 differentiated into nutritive, and the other into locomotor and 

 respiratory forms, thus constituting a link between the Protozoa and 

 Metazoa. He accounts for the ciliated cells becoming invaginated to 

 form part of the lining of the gastrula cavity, by supposin'4' that on 

 the ancestral sponge becoming fixed the locomotive ciliated cells 

 increased in size and number less than the nutritive, and so came to 

 line the cavity of the gastrula, some of the nutritive subsequently 

 passing in at its mouth. In the adult sponge he thinks the 

 descendants of the latter cells which line part of the canals to be 

 alone digestive, the collared cells, the descendants of the ciliated cells, 

 of the larva being mainly respiratory. 



Sponge - spicules. — In concluding an article on Plectronella pa- 

 pillosa, a new genus and species of Echinonematous sponge,§ Mr. W. 

 J. Sollas says that regarding the various kinds of sponge-spicules as 

 resulting from a variously modified cell-growth, the relations sub- 

 sisting between the chief of them may be embodied in a diagram. 



1. An elongate growth of the original cell in two opposite 

 directions at equal rates gives us the ordinary acerate spicule 

 (Fig. 1), which is biradiate (diactinellid) but uniaxial. 



2. A retardation of growth in one radius gives the acuate spicule 

 of Fig. 2. 



3. A linear growth in one direction only gives the acuate (Fig. 3) ; 



* N. S., vol. xix. (1879) p. 103. 



t " Untersuclmngen iiber d. Bail u. d. EutwiL-kelung der Spongien," 'Ztitschr. 

 f. wiss. Zool.,' vol. xxxi. (1878). 

 t Ibid., vol. xxiv. (1874). 



§ • Ann. and Mag. Nat. Hist.,' ser. 5, vol. iii. (1879) p. 23. 

 VOL. II. N 



