Pelagic Tunicata — Bary 
103 
TABLE 1 
The Ranges and the Ratios of the Lengths of Body and Tail of Oikopleura fusiformis from 
New Zealand 
LENGTHS (MM.) 
STATION 
NO. 
Body 
Tail 
RATIOS, BODY TO TAIL 
Maximum 
Minimum 
Maximum 
Minimum 
Maximum 
Minimum 
Average 
32 
1.2 
0.8 
4.3 
3.5 
3.6 
4.4 
4.0 
153 
1.1 
— 
4.1 
— 
3.7 
— 
3.7 
171 
1.1 
0.3 
4.8 
1.4 
4.4 
4.6 
4.5 
178 
1.4 
0.4 
4.5 
2.0 
3.2 
5.0 
4.1 
Averages 
3.7 
4.7 
4.1 
Oikopleura dioica (Fig. 2) is the only species 
so far described as being unisexual. This, to- 
gether with a long tail with two subchordal cells, 
stout trunk, a characteristic posteroventral blind- 
sac to the right stomach, but absence of blind- 
sac on the left stomach, are features of diag- 
nostic value ( see Table 3 ) . 
Aida ( 1907 ) gives the body length of his 
largest specimen as 1111 p , and the tail length 
as 3888 p, i.e., a ratio of body to tail of 3.5; 
Essenberg ( 1926^) states that the body length 
ranges from 0.5 to over 1 mm., and that the tail 
is "about four times the length of the trunk.” 
Thompson (1948) gives measurements of 0.3 
to 1.2 mm. body length, 1. 4-4.0 mm. tail length, 
the ratios of body to tail length being 4.7 and 
3.3 respectively. Thus the New Zealand material 
corresponds well with that from elsewhere (ex- 
cepting the ratio of 1:7.0 obtained for a small 
specimen with an abnormally long tail, captured 
at Station 12). 
Class II: ACOPA (CADUCICHORDATA) 
Subclass THALIACEAE 
Order PYROSOMIDA 
Family PYROSOMATIDAE 
Genus Pyrosoma Peron 
A detailed study of Pyrosoma by Metcalf and 
Hopkins (1919) is summarised and applied 
to Australian material by Thompson (1948). 
Sewell ( 1953 ) critically analyses these and other 
studies of the genus, and shows that many 
species and subspecies previously recognised are 
but growth stages of a relatively small number 
of species. 
Two species were present in the New Zealand 
material. One damaged specimen of P. spinosum 
was collected at Station 326; P. atlanticum oc- 
curred between Cook Strait and southern New 
Zealand, sometimes in very large numbers. 
Pyrosoma atlanticum (Peron) 
Pyrosoma atlanticum Metcalf and Hopkins, 
1919; Thompson, 1948; Sewell, 1953 
Specimens from the tetrazooid to colonies 
40 cm. long were present in moderate numbers, 
from the beginning of February. In March, 
and especially in April (collections partially 
FIG. 2. Oikopleura dioica, a mature male of 1.1 
mm. body length. 
