53 



When tlie larva has fouiirt its new host, it attaclies itself either beneath the cara- 

 pace to the branchiae or in the marsupiuni to one of its plates, to one of the gills, or simply 

 to the ventral surface of the body, or to the basal part of a leg, and iu case it attaches 

 itself to a not fiill-grown female of Ampliipoda. of course it must content itself with one of 

 the three last-mentioned places. The larvae of Aspidoecia fasten themselves either outside 

 on the dorsal surface of the host (an Erythrops), if they are growing into females, or on 

 a female of their own species (pi. XII, fig. 3 b), if they are going to be males. The fixation, 

 which is very solid, is etfected by a viscous substance, which expands itself so as to form a 

 larger or smaller plate on the fi'ont (pi. IV, fig. le, s; pi. VIII, fig. 2i; pi. XI, fig. 1 e, s). 

 This viscous substance must be secreted of a gland in the front part of the head, the orifice 

 of which, however, I have tried in vain to find; the gland itself must be studied from fresh 

 material. (It was pointed out long ago by several authors, that the larvae of various Caligidae, 

 of Achtheres etc., in their first stage fasten themselves in a somewhat similar manner by a 

 »Stirnband ' (Glaus).) The larva, after hinging itself in this way. relaxes the grip of its 

 limbs and hangs quite fi-ee; thereupon it begins to change form, bending forward the last 

 joint of the maxillae, and its cephalothorax getting gradually shoiter and broader (pi. XI, 

 fig. 1 e; pi. IV, fig. 1 e); how short and broad it may occasionally become, may be seen on 

 pi. IV, by comparing fig. 1 c, wliich represents a free larva, and fig. 1 d, which represents 

 a larva that has reached its full breadth, and which no doubt is going to develop into a 

 male; fig. le is an intermediate form shortly after the fixation. Then the muscles etc. in 

 all the limbs and in the abdomen dissolve themselves, and the contents of these oi-gans are 

 transferred into the cephalothorax, the muscles of which have also beeu dissolved, and finally 

 this united substance is suiTOUuded by a new skin under the old one. The subsequent 

 development will be treated in the next division. 



e. The post-larval Developraent; the Pupae. 



The post-larval development, wliich takes place between the larval stage just described 

 and the appearance of adult males and of females (wliicli, though very small, in all important 

 features resemble the egg-laying specimens), ofter the greatest deviations between the ditierent 

 forms, but, unfortunately, the representation I am capable of giving is very fragmentary. 

 The larva in many cases develops into a pupa, out of wliich evolves the female, and, in 

 some cases, the male; in other cases the male is developed immediately ft'oni the larva etc., 

 and in Mysidion the metamorphosis is more complicated. I know the complete development 

 only of two species of SphceroneUa and of Homoeoscelis minuta. but the two first-mentioned, 

 in particular, are fortunately very diftei-ent from one another; I know, moreover, the develop- 

 ment of the male in A.^'pidoecia. and of the females belonging to the species of the Sph<rr. 

 Leuckartii-grou\). Finally I have found a pupa of each of four other species of Sphirronella 



