BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 27. AFD. IV. N:0 6. 23 



and afterwards stained in a solution of acid-fuchsine, their 

 chief substance seems to be homogeneous and of a light rose- 

 colour. The cellulär elements within them are very sparse 

 and ramified, resembling in a certain degree those of connec- 

 tive tissue, but they also present an obvious conformity to 

 wandering plasma-cells intercommunicating by their pseudo- 

 podia. In the folds of the female tubes the corpuscles seem 

 to be present more abundantly. In my opinion most of them 

 are true migratory cells, a view supported by the facts that 

 they have around the nuclei, or in their vicinity, a various 

 number of larger and smaller vacuoles, and moreover, they 

 vary greatly in number in different places. Thus, for in- 

 stance, in many sections of male tubes especially, the cells 

 seem to be totally absent or nearly so. 



Durin g the increase of the sexual products, the free bör- 

 der of the folds in question gradually become more and more 

 swollen from the affluent nutritious blood, but, on the contrary, 

 during their ripening process there enters an apparent reduc- 

 tion in volume of the folds, which finally present themselves 

 as very narrow bands, or rather lists, along the inside of the 

 tubes (Pl. I, fig. 11). The number of the folds, commonly 

 four to six, seems to be subject to some variation. Moreover, 

 their arrangement appears to be somewhat different in the 

 two sexes. In the male tubes they are more irregular, and 

 the sexual cells become at a låter period of their development 

 not only spread över the glens but also över a greät part of 

 the folds themselves. 



A full grown but immature ovum measures about 0,5 mm. 

 in diameter. It is surrounded by a thin follicular capsule 

 formed by those cells which subsequently fused, thus forming 

 a membrane in which the nuclei alone remain distinct and be- 

 come placed on its outer surface. In his beautiful work on the 

 histological structures of the Echinoderms Hamann^ says: 

 "Zugleich scheiden diese Zellen eine Membran um die Eizelle 

 ab, welcher sie aussen aufliegen". In my opinion the follicle- 

 cells do not secrete any membrane, but their plasm become 

 fused into a plasmodium, thus constituting a membrane in 

 which the nuclei lie protruding exteriorly as small knobs (Pl. 

 I, fig- 1-2 f ). 



^ Beiträge zur Histologie der Echinodermen. I. Die Holothurien. Jena 

 1884. 



