Erik Nordenskiold 
165 
cance of which are two of the most difficult problems in the whole investigation. 
The fact is that at the stage in question there appear in the plasma-rod longi¬ 
tudinal folds, which are more colourable than the plasma itself, and as it seems, 
at least in some transverse sections, are formed by invagination of the surface 
(Figs. 28,29), from which it seems possible to conclude, that the cord mentioned 
above is formed in this way, by folding and separation of the fold from the 
surface. The spermia, which are always curved and folded, here prevent to a 
very great extent the observation of the process, but cross-sections, as mentioned 
above, make this interpretation of the conditions at least possible. 
Through the definitive location of the nucleus along the plasma-rod and 
the appearance of the above-mentioned cord the spermatozoon acquires the 
shape shown in the vas deferens of the male (Figs. 30, 31). At this stage we 
see the rod-like, laterally placed nucleus, the conical centrosomal corpuscle, 
united with the nucleus, the plasma-rod with its staining cord. The sperma¬ 
tozoon of the tick is, as shown bv this, atypical, and, like that of several 
crustaceans, cannot be compared with regard to its several components, with 
the common spermatozoon type. A desire to attain this object led me astray 
in my preliminary investigation, but the errors in my previous publication 
can easily be rectified by the results published here. 
The work, of which the results are herein published, was begun at the 
Zoological Laboratory at Marburg and finished after a long interval of time 
at the Zoological Institute at Christiania. To Professors Korschelt and 
Tonniges at Marburg and Bonnevie at Christiania I am much indebted for 
the helpful advice I have received during my work, for which I here beg to 
offer them my most respectful thanks. 
REFERENCES. 
Bonnet, A. (1907). Recherches sur l’anatomie comparee et le developpement des Ixodides. 
Ann. de VUniversite de Lyon. Lyon, n.s. fax. 20. 
Robinson, L. E. and Davidson, J. (1914). The anatomy of Argas persicus (Oken 1818). 
Part III. Parasitology, vi. (See pp. 413, 420, PI. XXVII, fig. 6 a-d. These authors 
merely state that spermatogonial cells give rise to four spermatids which are transformed 
into spermatozoa. The spermatids pass to the vas deferens where they rapidly assume 
the elongated form of the mature spermatozoa.) 
Samson, K. (1909). Zur Spermo-histiogenese der Zecken. Sitzungsber. der Gesellsch. natur- 
forschender Freunde. Berlin, Jahrg. 1909, No. 8. 
Note: —From the extensive literature on spermatogenesis may here be quoted only 
some authors that have been especially consulted in connection with the work, the results 
of which are here described; a great many others, that have only occasionally been consulted, 
may from considerations of space be omitted. 
Bonnevie (1904). Zur Kenntnis d. Spcrmiogenese d. Gastropoden. Biol. Zentralblatt, xxiv. 
- (1906). Beobachtungen fiber Keimzellen. Jenaische Zeitschr. xli. 
- (1906). Kimcellerne hos Enteroxenos. Archiv for Mathematik og Naturvidenskab, xxvii. 
Lee (1897). Les cineses spermatog6n6tiques chez Helix pomatia. La Cellule , xm. 
