MINUTE ANATOMY OF LIMNOCODIUM. 547 



nuclei of the sperm mother-cells of the first layer, but their 

 chromatin is in a more compact condition and stains more 

 deeply. The nuclear matter of these cells now apparently 

 undergoes a sort of condensation, as indicated both by dimi- 

 nution in size as compared with the size of the cell, and 

 also by greater intensity of tingibility (fig. 8, 7). At this stage 

 the cells apparently undergo a second division, but whether 

 by karyokinesis or not could not be ascertained, owing to 

 their extreme minuteness. In either case the result is — 



3. A number of cells (fig. 8, S) with very small, deeply stain- 

 ing nuclei, which, by the drawing out of their protoplasm into 

 the tail, give rise to — 



4. The spermatozoa themselves (fig. 8, e). The spermatozoa 

 are of the ordinary hydroid type, with well-marked heads and 

 relatively short tails. They probably escape to the exterior by 

 the dehiscence of the outer epithelium of the spermaria. 



At stage 3 the cells seem to become segregated into groups. 



The process of spermatogenesis, as described above, is 

 totally at variance with the views of Andre de Varenne (5) 

 regarding the condition of the nucleus of the sperm-cells. De 

 Varenne makes the following statement: — "Dans toute la 

 duree du developpement des spermatozoides, en prenant la 

 cellule mere des son debut, le noyau n'a pas change.^' Limno- 

 codium certainly aflPords us a most eff'ective refutation of any 

 such view, if any further objection to the view was needed after 

 the extensive researches of Thallwitz (6) on hydroid sperma- 

 togenesis. 



Conclusion. 



In conclusion, I am afraid that the foregoing observations 

 do not shed very much light upon the question of the systematic 

 position and genetic affinities x)f Limnocodium. It is seemingly 

 a case in which an increase of knowledge is correlated with an 

 increase of difficulties. All attempts to find a resting-place for 

 Limnocodium in the system of Haeckel have been unsatisfac- 

 tory. Of the four sub- orders into which the Medusae are 

 divided by Haeckel, neither the Authomedusse nor the Narco- 

 medusse can receive Limnocodium on account of the position 



