No. 2.] THE MORPHOLOGY, OF DERO VAGA. 143 
somewhat from the form described by Leidy, while the latter 
form is very closely related to the other species of Dero and 
without doubt should be classed with them. 
Vaillant! and Beddard? classify the annelid as Dero vaga Leidy. 
- The following synopsis is taken from Beddard’s monograph: 
FAMILY NAIDOMORPHA. 
Definition. — Aquatic Oligochaeta of small size. Setae usually in four 
groups upon each segment, sigmoid, bifurcate, hastiform, and capilliform. 
Sexual reproduction at fixed intervals, between which asexual reproduction 
by fission occurs. Sexual organs (only known in a few types) are situated 
far forward, commencing even in the fifth segment. 
This family of Oligochaeta comprises the following recognizable genera : 
(1) Chaetogaster Baer. (5) Pristina Ehrenberg. 
(2) Amphichaeta Tauber. (6) Uncinats Czerniavsky. 
(3) Wazs O. F. Miiller. (7) Chaetobranchus Bourne. 
(4) Bohemilla Vejdovsky. (8) Dero Oken. 
GENUS DERO Oken. Syn. Proto Oersted. Uvonats Gervais. Xantho 
Dutrochet. Azlophorus Schmarda. JVazs O. F. Miller (in part). 
Definition. — Dorsal setae capilliform and hastiform,® commencing upon 
the sixth segment. Branchial processes present at hinder end of body. 
Eyes absent. Inhabit tubes. 
He notes eight species as follows: 
D. miilleri Bousfield. D. limosa Leidy. 
D. furcata Oken. D. perrieri Bousfield. 
D. obtusa D’Udekem. D. vaga (Leidy). 
D. latissima Bousfield. D. multibranchiata Stieren. 
DERO VAGA (Leidy). Azlophorus vagus J. Leidy. Am. Wat., 1880, 
p- 423. D.vaga L. Vaillant. Aznelés, p. 383. 
Definition. — Length about 8 mm.; number of segments, 25. Body ending 
in two long processes; branchiae rudimentary, only two slight processes. 
Dorsal setae bundles consisting of one capilliform and two pectinate setae.4 
Perivisceral corpuscles present. Contractile hearts in VIII, IX, and X. 
fZab.— North America; Trinidad. 
1L. Vaillant, Histoire naturelle des Annelés Marins et d’Eau douce, Tome 
III, Paris, 1889. 
2 F. E. Beddard, Monograph of the Order Oligochaeta, Oxford, 1895. 
8 Palmate setae may also be present in the dorsal bundles. 
4 The setae in the dorsal bundles are more nearly palmate than pectinate, and 
there are usually two capilliform and two palmate in a bundle. Occasionally 
three of each are present. (Notes are mine.) 
