224 THE VOYAGE OF H.M.S. CHALLENGER. 



P. Cavity of the sac of the zooid, occupying, iu the recent condition, the 

 wide upper chamber of the dactylopore. 



D'. Another dactylozooid, seen in section. The zooid, being doubled 

 back into the outer part of the dactylopore where cut in section, 

 its cavity appears partly as a lumen at T", partly as an elongate 

 hollowed area, in which are seen the strong longitudinal retractor 

 muscles of the zooid. 



C, C. Tortuous canals, offsets of the general ccenosarcal meshwork, which 

 pass radially outwards in the substance of the pseudosepta, between 

 the pores of the dactylozooids. The canals ramify as they reach 

 the outer margin of the calicular system, and join by their branches 

 the superficial outer network of the coenosarc. 



N. Large ovoid nematophore, full of closely-packed nematocysts. One 

 such nematophore is present in each interval between the outer 

 margins of the mouths of the pores of the dactylozooids. 

 Fig. 3. Earliest stage in the development of the ovum in Cryptolielia pudica. 



A bucblike mass of endoderm cells is gathered together within an offset 

 of a branch of the ccenosarcal meshwork. 

 Fig. 4. The same, in a further stage of development. 



0. Ovum, with germinal vesicle and spot. 



S. Spadix, composed of endoderm cells. 



E. Thin layer of the ectoderm, continuous with that covering the spadix, 

 and investing the free surface of the ovum. 

 Fig. 5. Section through a planula of Cryptolielia pudica, in a very early stage. 



E. Ectoderm. 



En. Endoderm. 

 Fig. 6. Portion of a planula of Cryptolielia pudica, in a more advanced stage than the 

 foregoing, viewed from the outer surface. 



E. Ectoderm, transparent, and showing a demarcation into the poly- 

 gonal areas. 



En. Endoderm cells, seen through the transparent ectoderm. 

 Fig. 7. Section vertical to the surface of a planula of Cryptolielia pudica when fully 

 developed and ready for exit from the broad sac. 



En. Endoderm, composed mainly of oily globules. 



E. Ectoderm, which is extremely thick, and for the most jmrt trans- 

 parent and gelatinous in appearance. 



N, N. Nematocysts. 



A. Tracts composed of small, rounded, non-transparent ectodermal 

 elements, which run from the endoderm region at intervals ver- 



