ANDREWS: ANNULUS VENTRALIS. 
473 
tacle is homologous in structure and ontogeny to the annulus. As the 
annulus is found only in the most specialized crayfish and as compara¬ 
tive anatomy would connect the less specialized crayfish with marine 
forms, leading to the lobsters, it seems most probable that these two 
similar sperm receptacles have been independently evolved in Cam- 
barus and Homarus. 
Looking through the interesting series of cases of indirect sperm 
transfer exhibited by scattered representatives of several of the great 
groups of animals we find one other animal in which sperm is stored 
in pockets on somites at a distance from the oviducts and later set free 
into a secretion that envelops the eggs when they are laid. This 
animal is the earthworm and we can scarcely suppose its sperm re¬ 
ceptacles to have had an origin in common with those of Cambarus. 
or of Homarus. 
Problems and Speculations. 
The characters of the five annuli studied are in general in harmony 
with the arrangement of these species as proposed by Ortmann (: 02). 
Cambarus clarkii is one of Ortmann’s group I, or simplest Cambari; 
C. bartoni is in group III of complex species; and C. afjinis, C. immunis,. 
and C. virilis are all in group IV of highly specialized forms. 
Comparing the annuli of these five species we find that in C. clarkii 
(pi. 47, fig. 34; pi. 48, figs. 36, 39, 40) the sperm pocket is a simple 
longitudinal one without any ‘recess’ or any vestibule; that in C. 
immunis (pi. 48, figs. 45, 46, 48) the pocket is a simple transverse 
one without any ‘recess’; that in C. bartoni (pi. 48, figs. 41, 42; pi. 
46, fig. 26), it is very similar to the last, but has a ‘recess’; that in C. 
virilis (pi. 47, figs. 29, 31; pi. 46, figs. 21, 23) it is a very long, com¬ 
plex, longitudinal pocket with a ‘recess’; and that in C. affinis (pi. 
43, figs. 1, 2, 5, 6, 8, 10) there is a short semitransverse pocket with 
highly specialized ‘recess’ and greatest development of external 
sculpturing. 
From a primitive lengthwise pocket as in C. clarkii greater com¬ 
plexity might result by elongation and folding, as in C. virilis or by 
elaboration of a lateral orifice, as in C. immunis. A highly specialized 
annulus like that of C. virilis might arise secondarily by suppression 
of the anterior part of the pocket and development of tuberosities 
from the lateral ridges. 
