MORPHOLOGY AND SYSTEMATIC POSITION OF SPONGIDA. 103 



former, very large, so that the peculiar contents of the 

 nuclei are bounded by a proportionally delicate sheath. 



Near these moving AmoebEe tolerably large cysts are fre- 

 quently found ; they undoubtedly take part in the reproduc- 

 tive process of these organisms. The cysts (fig. 26 d) are 

 always quite round, with a tolerably delicate sheath lying 

 close to the contents. The diameter is somewhat variable, 

 usually about 0*03 — 0'04 mm., and in one case 0007 mm. 

 The protoplasmic body contained in the sheath always con- 

 sists in part of a very clear and quite homogeneous proto- 

 plasm, and in part of a very finely granular protoplasm. 

 Inside the cyst a number of nuclei are invariably found, 

 they are of the same nature as the smaller nuclei in the 

 ordinary Amoeba condition. The author has counted 11, 

 19, and occasionally 25 or even 30 small nuclei. The size of 

 these nuclei varies somewhat in one and the same cyst, so that 

 the measurements taken vary between 0*003 — 0*008 mm. 

 The investigations which have been as yet made do not 

 afford any clear evidence of the relationship of the single to 

 the multi-nucleated condition. 



On the Morphology and Systematic Position of the Spon- 

 GiDA. By F. M. Balfour, M.A., Fellow of Trinity College, 

 Cambridge. 



Professor Schulze'sI last memoir 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. The facts which 

 have been thus established have suggested to me a view of the 

 morphology and systematic position of the Spongida, somewhat 

 different to that now usually entertained. In bringing forward 

 this view, I would have it understood that 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. 



To render clear what I have to say, I commence with a very 

 brief statement of the facts which may be considered as estab- 

 lished with reference to the development of Sycandra raphayms 



' " Untersuclmngen iiber d. Bau u. d. Entwickelung der Spongien," ' Zeit. 

 f. wiss. Zool.,' Bd. xxxi, 187S. 



2 "Zur EntwickeluDgsgeschicbte der Kalkschwamme," 'Zeit, f. wiss 

 Zool.,' Bd. xxiv, 1874. 



