584 The American Naturalist. [June, 
the ectoderm, containing numbers of large cells filled with thread cells. 
Herdman confirms the view, lately disputed, that the hepatic ceca 
are in communication with the exterior v/a the connecting tube and 
the external orifice of the cnidiphorous sac. 
Zoological News.—General.—C. F. Marshall returns to the 
discussion of the histology of the muscle fibre.' After a discussion of 
some of the recent literature and a reply to Rollett’s criticisms of the net- 
work theory, Marshall reaffirms his belief in the view that in rapidly 
contracting muscles (transversely striated) the portions differentiated to 
perform the contraction form a regular and highly modified intracel- 
lular network the longitudinal fibres of which produce the contractions, 
while the transverse meshes give the striated appearance to these muscles. 
He farther describes the development of the network in the trout and 
rat, and concludes that its transverse portions are directly connected 
with the muscle corpuscle, the longitudinal with the nerve end. The 
network developes first at the surface, and extends centripetally, and 
each muscle fibre appears to be developed from a single cell. 
Worms,.—Chetobranchus is a new genus of Oligochztes described ? 
by A. G. Bowman from fresh water of Madras. It is remarkable in 
having elongate processes (a pair to a segment) on the dorso-lateral 
portions of the body. These processes diminish in length from before 
backward, until at about the middle of the body they appear as mere 
warts upon the surface. As each contains a loop of the lateral blood- 
vessel as well as a diverticulum of the ccelom (and some of the dorsal 
setze) they are regarded as respiratory in function. Reproduction by 
fission was observed, but no budding zone was recognised. 
Arthropoda—A. D. Michael has been studying the variations in 
the female reproductive organs of Uropoda, 3 a genus of Acarina. In 
these forms the ovipositor is replaced by a “‘ vestibule’’ leading from 
the vagina to the exterior. This structure is quite complicated, and is 
surrounded by complex organs. In U. ovalis these structures are ar- 
ranged so that during copulation the spermatozoa pass,into the recep- 
taculum seminis, but are prevented from entering the vagina, while later 
they may be forced into the latter organ. In U. vegetans the relations 
are much the same. In U. krameri the vestibule is adapted for strip- 
ping the shell from the egg at the time of laying, so that the larve 
emerge from the egg at the time of oviposition. 
Quart. Jour. Micros. Sci., XXXI, p. 65, 1890. 
2 Quart. Jour. Micros. Sci., XXXI, p. 83, 1890. 
3 Jour. Roy. Micros, Socy-, April, 1890. 


