982 HISTOLOGY AND NERVOUS SYSTEM OF CALCAREOUS SPONGES, 



THE GLAND CELL8. 



Similar cells as those described from a few other Sponges, and 

 to which a secretory function is attributed, are also met with in 

 the (''alcareous Sponges. 



Either single or in small bunches they are attached to the inner 

 side of the Ectoderm of the Lencones. They are pear-shaped, and 

 their real nature can easily be detected by the presence of large 

 highly refractive granules in their interior. They stand vertical to 

 the surface with which they are in connection by a .slender 

 peduncle. 



SENSITIVE AND GANGLIA CELLS. 



Spindle-shaj)ed cells of the Mesoderm, which lie just below the 

 surface, and protrude beyond the outer coating of Ectodermal 

 pavement cells are not rare in the Heteroccela. They stand vertical 

 to the surface, the nucleus is oval and situated in the middle of the 

 cell. The proximal part of such a cell is often produced into a long 

 thread, which may be ramified and often can be traced to another 

 cell lying further down in the Mesodermal Gallert. Such spindle- 

 shaped cells have been observed by me in clusters scattered 

 irregularly over the surface in Leucandra saccharata Leucandra 

 meandrina and other species. Single and also scattered irregularly, 

 but particularly numerous in the vicinity of the pores in Leucandra 

 conica,n.s.,and Leucandra sacharata, also in Lencetta and Leucaltis. 

 As a ring surrounding the inner wall of the conic, widening 

 canal leading down from the pores of Sycandra arborea into the 

 inter canals. As clusters in the same locality in Grantessa sacca, 

 n. s. Also, in Vosmperia gracilis, n. s., and Sycandra pila, n. s. 

 I have detected similar structures in bunches around the pores, 

 these latter are however, slightly different from the former, and 

 I do not like to assert their nei'vous nature with the same con- 

 fidence as that of the former organs. 



It appears from this, that sensitive cells of this kind are met 

 with in all Heteroccela. In Homoccelia I have not found any 

 cells which may be considered as specially sen s tive 



