LANÜGINELLA PUPA. 15 



the chamber-wall as well as that of areliseocytes and of trabeculie 

 arising from the chamber-rim, I must state at once that it is to 

 a great extent a failure, in part due to the unsuccessful lithograph- 

 ing and in part to the highly unsatisfactory state of the origi- 

 nal preparation.'-' 



The chambers are shallow and cup-like or long and thimble- 

 like or tubular. Their diameter, 77-132 r- ; on an average 100 ,"• 

 Length, up to 440 />«. The longe.^t are found at the blind ends 

 of excurrent canals, in the periphery of the choanosome ; they 

 may sometimes present a lobed or branched appearance. All the 

 more deeply situated chambers are cup-like. In all my prepara- 

 tions, the cham])er-wall appears at the best as a faintly stained 

 reticulum with minute irregular meshes. The nuclei are not 

 discernible under ordinary powers of the microscope ; Init by 

 using an immersion system they can, under favorable circum- 

 stances, be recognized as ill-defiued spots found at short intervals 

 and measuring not more than 2 /< across. In staining capacity 

 they differ scarcely at all from the substance of the reticulum. 

 Flagella seem to be in no case preserved. 



The trabecuhp are developed in moderate, and in some 

 individuals in very great, abundance, (^n the external sponge- 

 surface they are frequently spread out in a film-like manner to 

 form the perforated dermal membrane. The nuclei are minute 

 but distinct, l)eing well stained as usual. Not seldom have I 

 seen, hanging on the trabecuL'e, homogeneous fat-like spherules 

 which stained well with both carmine and hœmatoxylin ; they 

 were no doubt the product of the thesocytes. 



* Many of the plates, now issued in liiis Contribution, were prepared and printed 

 several years ago in the early period of ray studies anfl therefore contain shortcomintr^ of 

 which I am more conscions than ever. For them I hcg to ask a lenient judgment. 



