644 A Remarkable Life History and its Meaning. (November, 
pretty closely in size and organization, but differing in outline 
and in some other slight details. 
than 
=i 
VOIR UUR 
C EAL nae 
i 
1 ‘ a 
| ii 
KE 
44. Adult solitary Salpa, 
ndo 
style ; n, gill; nu, “ nucleus ” or di- 
gestive organs ; r, heart; u, chain of 
males. 
(Compare Figures 43 and 45.) 
One of these forms, that shown in 
Figures 43 and 44, is called the 
“ solitary Salpa,” since each animal 
is entirely independent of all the 
others; while those of the other 
form (Figure 45) are called “ chain- 
salpæ,” since they are usually found 
united in a chain. Twenty-five 
or more of the barrel-shaped bodies 
are placed in a row, end to end, 
and each one is fastened to its 
neighbors before and behind it; 
this row is placed beside another 
similar to it, and each animal is 
fastened to two of its neighbors in 
the other row, so that the whole 
group of fifty or more forms @ 
chain something like two trains of 
cars side by side on parallel tracks; 
only, to make the comparison 
more perfect, we must imagine 
each car chained to two cars mM 
the other train, as well as coupled 
to those before and behind it. 
Since the animals are fastened in 
such a way that the posterior 
openings of all point in the same 
direction, all the streams of dis- 
charged water are driven in the 
same way and the whole cham 
moves forward with a uniform, 
steady motion. Figure 47 shows a few of the Salpz from a chain, 
at a very early period of development, but as 
the animals are, 
unfortunately, not sufficiently far advanced at this time, the 
figure fails to give a very clear idea of the way in which they 
are united. 
Salpa is very remarkable for the number of examples it pre- 
sents of deviation from laws which are almost uniformly ¢on- 
formed to throughout the animal kingdom. 
One of the mos 
striking of these anomalies is the periodical reversal of the actio? 
cea E 
