64 CRUSTACEA——COPEPODA CHAP. 
are three genera, Monstrilla, Haemocera, and Thaumaleus. The 
best known type is Haemocera danae (often described as Monstrilla » 
danae). In the adult state (Fig. 30) there are no mouth-parts ; the 
mouth is exceedingly small and leads into a very small stomach, 
which ends blindly, while the whole body contains reserve food- 
material in the form of brown oil-drops. The sole appendages on 
the head are the first an- 
tennae; but on the thorax 
biramous feet are present by 
means of which the animal 
can swim with great rapidity. 
This anomalous organisation 
receives an explanation from 
the remarkable development 
through which the larva 
passes. The larva is liberated 
Fic. 30.—Haemocera danae, x 40. A, Side Fic. 31. — Free-swimming Nauplius 
view  ; B, ventral view g. Ant.Z, 1st an- larva of Haemocera danae; Ant.1, 
tenna; e, eye ; ov, ovary ; ovd, oviduct ; Sf, Ant.2, 1st and 2nd antennae ; e, 
stomach ; Zh.Z, 1st thoracic appendage ; remains of eye; Md, mandible. 
Th.5, 5th thoracic segment ; vd, vas deferens. (After Malaquin.) 
(After Malaquin.) 
from the parent as a Nauplius with the structure shown in 
Fig. 31; it does not possess an alimentary canal. It makes 
its way to a specimen of the Serpulid worm, Salmacina dysteri, 
into the epidermis of which it penetrates by movements of the 
antennae, hanging on all the time by means of the hooks on 
the mandibles. From the epidermis it passes through the 
muscles into the coelom of the worm, and thence into the 
blood-vessels, usually coming to rest in the ventral blood- 
