54 



(S. Argissce, S. longipes, S. microcephala and S. insignis), numerous pupae of Choniostoma 

 mirabile, and three different stages of development of Mysidion commune. 



Let us begin with the simplest form of development. On a completely adult female of 

 Aspidoecia Normani, sitting on the dorsal surface of the abdomen of Erythrops serratus 

 G. 0. Sars, I found four larvae attached (pi. XII, fig. 3 b, where one of the larvae is left 

 out and two of the others designated by a v.) One of these came off easily, when touched, 

 and it appeared that its skin had begun to burst along the lateral margin; on a closer 

 examination it burst somewhat more, and it proved to contain a full-grown male. In this 

 state the preparation is illustrated in pi. XII, fig. 3 m. The spermatothecae of the male 

 were filled, and it had a very short and very thick frontal thread (s). This instance suffi- 

 ciently proves, that the male develops itself directly in the larva, without the intermediate pupa 

 stage and without a second moult. I also found a single larva, which had placed itself 

 directly on the carapace of the host, but its examination gave no result, its development not 

 being far enough advanced. However, I have found exceedingly small females sitting on 

 different parts of the host, and I have not the slightest doubt that the larvae which are 

 going to become females, attach themselves directly to the host, though I do not know, 

 whether they pass through the pupa stage or change directly into females, yet I feel 

 inclined to accept the latter alternative, seeing that the parasite sits on the outside of its 

 host, thereby running the risk of falling off very easily. 



"We now come to a species in which both sexes pass through a pupa stage, namely 

 Splicer. Giardii (pi. VI, fig. 3 i, fig. 3 k and fig. 3 1). I have found three male pupae and 

 not a few female ones. The body is of a short ovate shape; the males are more oblong and 

 smaller, -125 mm. in length (fig. 3 k), the female pupae stouter and varying in length between 

 '125 mm. and '142 mm. (fig. 31, which is drawn on the same scale of enlargement as fig. 3 k). 

 In the female the foremost two thirds of the ventral surface form a broad, naked, odd area, 

 whereas the whole remainder of the body is closely covered with rather short hairs. The 

 male pupa is covered with hairs like the female, except that part of the back which corre- 

 sponds to the head and the upper parts of its lateral surfaces, which are naked (fig. 3 k). 

 Fig. 3i shows a male pupa from below, fig. 3 k from the side; the antennulse (a), the 

 antennae (c), the maxillulae, the maxillae, the maxillipeds, the trunk-legs and the caudal sty- 

 lets are seen as naked, smooth, pouch-shaped processes, whereas the mouth is developed as in 

 the adidt animal; in front of the mouth we notice a semicircular, rather vaulted and prominent 

 area, and between the maxillae and the maxillipeds two pairs of oblong, somewhat prominent 

 knots, corresponding with the sub-median skeleton. The female pupa has also a free mouth 

 and all the same processes and projecting parts as the male, from which, however, it is 

 easily distinguished, not only by the above-mentioned difference in the extent of the hair- 

 coat, but also by the size of the processes which stand in the place of the trunk-legs, and 

 which are very small, whereas in the male pupae these organs — especially the first pair 

 — are much larger and furcate at the end This difference between the trunk legs, which 



