in the Daphniadse and allied Crustacea. 447 



not merely on its own account, but more especially because by 

 its means we get a new relation of these animals to the Cirri- 

 pedia *. Even Strauss-Durckheim remarks, with regard to the 

 cephalic tubercle (Kopfzapfen) described by him, that it may be 

 compared with the stalk of Lepas ; and, in fact, we need only 

 imagine it more strongly developed and constantly adherent, to 

 develope the structure just mentioned from it, and thus to 

 approximate our Entomostraca very considerably to the Cirri- 

 pedia. The resemblance would be a perfect analogy, if the 

 statement of Thompson (Zool. Researches, i. part 1) the first 

 discoverer of the metamorphosis of the Cirripedia f should be 

 confirmed, that the bivalve-shelled larvae of these animals adhere 

 by the back, and that the future point of attachment may be 

 detected in the suture between the shells, even in specimens 

 which are still swimming freely about. 



In opposition to these statements, however, it must not be 

 concealed that, according to other observers, the attachment of 

 the Cirripedia is not effected by the back, but by the antennse, 

 which likewise bear a small sucking disk at their extremity. 

 This is the opinion especially of the most recent and thorough 

 investigator of the Cirripedia (Darwin), who regards the stalk of 

 the Barnacle as the anterior part of the head, and in some forms 

 detected two persistent antennse at its extremity. 



Of course mere arguments from analogy cannot be set in 

 opposition to such definite statements ; but we cannot suppress 

 the observation that the morphology of the Cirripedia is not yet 

 perfectly cleared up, even after the minute investigations of 

 Darwin. There are gaps also in the observations, and that exactly 

 at the most important points for the decision of the question 

 before us. 



EXPLANATION OF PLATE XVI. B. 



Fig. 8. Evadne polyphemo'ides, Leuck., n. s. 



* It is possible that the filiform adhesive apparatus on the forehead of 

 Chalimus and some species of Caligus should also be regarded as the 

 analogue of the dorsal sucker in the Daphniadee. Recent investigations 

 by Hesse (Comptes Rendus, xliv. p. 1254) prove that the young Lernece 

 also adhere for a time by a frontal filament of this nature. 



t Slabber, however, had already seen and figured the larvae of a Bar- 

 nacle (Naturk. Verlust. pi. viii. fig. 3), but without recognizing their 

 nature. He saw these little animals escape in countless numbers from the 

 opened shell, and regarded them as parasites. 



