THE ANNALS 
AND 
MAGAZINE OF NATURAL HISTORY. 
[FOURTH SERIES. } 
No. 86. FEBRUARY 1875. 
XIT1.—Zoologico-Embryological Investigations. 
By M. Ussow*. 
“ Developmental history is the true light-bearer for investigations upon 
organic bodies.,.—Von Barr (Ueber die Entwickelungsgeschichte der 
Thiere, 1828, Bd. i. p. 281). 
DurinG my residence at Naples and Messina (1871-73) I 
turned my attention particularly to the exact investigation of 
the anatomy and developmental history of two extremely 
interesting classes of Invertebrate animals, namely the Cepha- 
lopoda and the Tunicata. In various species of the Cepha- 
lopoda I studied the structure of the female sexual organs, and 
the formation of the ova, and then, in four species, I traced 
the embryonal development from the fecundation of the ovum 
up to the complete development of the young. 
In the various species of the Tunicata I endeavoured to 
investigate :—1, the anatomy, the minute structure, and the 
postembryonal process of metamorphosis of the central and 
peripheral nervous system ; 2, the structure and in part also 
the mode of formation of the organs of sense; 3, the body- 
wall (the outer and inner mantle); 4, the circulatory system 3 
and lastly, 5, the digestive apparatus, with all its glandular 
appendages. 
As I am at present engaged in the detailed description of 
the by no means uninteresting facts that I observed, I think 
that a brief statement of the results obtained, such as I here 
propose to give, may not be without its use. 
* Translated by W.S. Dallas, F.L.S., from the ‘Archiv fur Naturge- 
schichte,’ xl. (1874) p. 328. 
Ann. & Mag. N. Hist. Ser. 4. Vol. xv. 7 
