326 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Blood System. 
Lang (’94, p. 546) says: “Unter den Acarinen ist ein Herz bis 
jetzt nur bei Gamasiden und bei Ixodes aufgefunden.” Griffith 
(’92, p. 146) states: “In those Arachnida which breathe only by 
tracheae the circulatory apparatus is rudimentary, there appears to 
be a simple dorsal vessel without arteries or veins and it may be * 
remarked that in some species the heart or dorsal vessel appears to 
be entirely wanting.” 
In all the tick preparations but one, the latter part of Griffith’s 
statement seemed to hold. In one series of cross sections, how¬ 
ever, of a female of about 5 mm. in length, there is a delicate aggre¬ 
gation of flattened cells on the dorsal side of the animal in the 
median plane just beneath the hypodermis. This mass of cells has 
an irregular cavity in its center in nearly every section. The cavity 
is much wider from side to side than dorso-ventrally and the whole 
indicates a tube much flattened dorso-ventrally, extending poste¬ 
riorly about a millimeter from the connective tissue sheath sur¬ 
rounding the brain. The ovary in this specimen was immature, 
so that the diverticula of the alimentary canal and the other organs 
of the body were not compressed by eggs, and it may be that this 
elongated tube is the simple dorsal vessel spoken of by Griffith. 
Since, however, no other series showed these appearances, it may 
be no indication of a blood system in Boophilus. 
Nervous System. 
I have little to add to the description of the nervous system as 
given by Pagensteclier for Ixodes. There is but one large ganglion 
surrounding the esophagus (pi. 18, fig. 4; pi. 19, fig. 7, hr,). This 
is covered by a connective tissue capsule. The cortex of this brain 
is a thick layer of nuclei of nerve cells and the center is a mass of 
fibers. 
No nervous connection was found between the appearances on 
the side of the scutum, which are called eyes by Salmon and Stiles, 
and the brain mass. 
The porose areas which have been shown on the dorsal side of 
the base of the female capitulum (pi. 18, fig. 2 ,por. ar.) are pecu- 
