CONTRIBUTIONS TO THE EMBRYOLOGY OF NEMERTEA. 417 
Contributions to the Embryology of the 
Nemertea. 
By 
Prof. A. A. W. Hubrecht, 
Of Utrecht. 
With Plate XXII. 
I. Tue DeEvELOPMENT oF LinEus Osscurus, Barr. 
It is a well-known fact that the development of Lineus 
obscurus, first inquired into by Desor in 1848, is characterised 
by the appearance of a larval form, to which the name of 
Desor’s larva has since been given. MacIntosh (17), Max 
Schultze (6), and Barrois (21), the latter more exhaustively, 
have since reinvestigated the development of this species. 
Their researches were carried on by means of larve that had 
first been rendered transparent, i.e. by so-called optic sections. 
Having succeeded in making actual sections through all the 
different phases of development, and having ascertained that 
by the aid of this method we may obtain far more reliable data, 
I venture to return once more to the same subject, since I 
have convinced myself that the results made known by former 
observers are to a large extent incomplete, and must on various 
points be abandoned and replaced by such as are furnished by 
the more perfect modern method. 
The outcome of my own investigations has already been fully 
published in the Dutch language,! in a treatise in quarto, printed 
1 «Proeve eener ontwikkelungs geschiedenis van Lineus obscurus, Barrois, 
door Dr. A. A. W. Hubrecht, Prys verhandeling met goud bekroond en nit- 
gegenen door het provinciaal Utrechtsch gerootschap van Kunsten en 
Wetenschappen,’ Utrecht, 1885, 4to. 
