54 KOLLIKER, ON MUSCULAR FIBRE. 
ments, in consequence of which the enveloping membrane 
is ruptured. . 
The development of the greater part of the iiternal organs, 
except the intestine, appears to take place after the escape of 
the embryo from the egg. No trace of the nervous system 
is at that time apparent, and but one pair of lateral fins 
exists. 
The following summary contains the main points of Gegen:. 
baur’s observations. . 
1. The products of segmentation of the vitellus are 
elongated pyramidal cell-forms, which retain this character 
even after the appearance of the rudiment of the embryo. _ 
2. The formation of the rudiment of the intestinal canal 
accompanies the segmentation of the vitellus. 
5. The intestinal canal appears at first as a central vitel- 
line cavity, its opening externally being a secondary process. 
4. The development takes place without any metamorphosis, 
and even without the appearance of cilia on the surface of 
the embryo. 
After a short discussion of the views of various authors 
respecting the systematic position of Sagitta, and a review 
of the principal points, chiefly embryological, connected with 
this still doubtful question, Gegenbaur concludes with ob- 
serving that the “genus Sagitia must be regarded as the 
representative of a special subdivision between the Nematoda 
and Annelida, and which might be designated the “ Pfeil- 
wurmer ” or “ Arrow-worms.” 
The paper is accompanied with figures illustrating the 
process of development. 
On the DrvetopMent of the TransvERSELY STRIATED 
Muscurar Fisre, in Man, from Simpte Criis. By 
Professor A. KOLLIKER. 
(Siebold and Kolliker’s ‘ Zeitsch. f. w. Zool.,’ vol. ix, p. 129.) 
Te extensive prevalence of unicellular muscular fibres or 
of contractile fibre cells in the Invertebrata having been de- 
monstratively shown, I was induced to inquire whether the 
mode of formation first noticed by Lebert, and afterwards 
by Remak, in the transversely striated muscular fibre of the 
