Pacific Salpidae — YoUNT 
303 
even touch; muscles extending far toward 
ventral surface. Ventral lip sphincter 4 (M 
bs) continuous. Ciliated groove (Fig. 14^): An- 
terior to M I, usually forming a large incom- 
plete circle. Viscera: Gut compact, in condi- 
tion C (Ihle and Ihle-Landenberg, 1933); 
embryo on right side dorsally between M V 
and VI. 
The form tuherculata of Metcalf has not 
been found in the collections studied. 
Individuals of the species of Salpa (solitary 
form) smaller than 2 centimeters have char- 
acteristic features. The two species can be 
distinguished by the presence in 5. maxima 
of a large elaeoblast and cavity, a large ciliated 
groove with three bends, the usually separated 
muscles, and the absence of a ventral hook 
on the dorsal posterior test projection, where- 
as S. fusiformh has opposite characteristics (ex- 
cept for the presence of an elaeoblast in very 
young animals). When the animals are larger, 
these distinctions become gradually less ap- 
parent; the elaeoblast becomes reduced or 
resorbed, although in all specimens of 5. 
maxima its test cavity remains; the ciliated 
groove of large S. fusiformis (47 mm. maxi- 
mum length of POFI specimens) may have 
the same structure as that of S. maxima; the 
body muscles may either be grouped or dis- 
tinct in both species; the internal "baumform- 
igen Fortsatzen” may be absent in 5. maxima; 
large individuals of 5. maxima may develop 
a ventral hook on the dorsal posterior test 
projection exactly as in S. fusiformis (Fig. 13/). 
Attachment organs, test, ganglion and eye, 
stolon, gut, and endostyle are either the same 
in both species or inter grade between them. 
The only structure that I have found never 
to intergrade is the cavity in which the elaeo- 
blast lies in S. maxima. In all specimens ex- 
amined, the elaeoblast cavity, although re- 
duced in larger individuals, was present when 
the. animal was considered, by other means, 
to be S. maxima. In all specimens considered 
to be S. fusiformis, even those as small as II 
millimeters, neither the elaeoblast nor its 
cavity was present. In small S. fusiformis the 
ciliated groove is a simple open one; in S. 
maxima, even in advanced embryos, the cili- 
ated groove is large and possesses the char- 
acteristic three bends. Thus, the most impor- 
tant differences between the two species are 
(1) the presence in 5. maxima of an elaeoblast 
cavity (both large and small individuals), and 
(2) the structure of the ciliated groove. 
As a result of insufficient descriptions, it 
is impossible to determine from the literature 
whether the asperate forms described and fig- 
Fig. 15. Mouth musculature of left side, seen from 
inside, a, Salpa maxima agg. ; b, Salpa fusiformis agg. 
