THE MORPHOLOGICAL DERIVATION OF THE COMPLEMENTAL MALE. 229 



searches of Lacaze-Duthiers (No. 51), is the member of this group 

 which we know best. The animal is surrounded by a large mantle 

 which here shows direct relation to the shell-valves of the Cypris 

 stage ; each half contains between its two lamellae not only the 

 hepatic outgrowths of the intestinal canal, but also the ovaries. 

 The body proper appears very much reduced, but is still distinctly 

 segmented, the mouth-parts are adapted for sucking, the six (or 

 five) pairs of thoracic limbs have degenerated, and the abdomen is 

 short. It should be mentioned as a characteristic of the group that 

 the first antennae are here never used, as in other Cirripedes, for the 

 attachment of the body. For the general morphological elucidation 

 of these forms indeed, we must compare them not with the adult 

 Lepas, but rather with the free-swimming Cypris larva. 



Very little has been made known, up to the present time, of the ontogeny of 

 these forms. The cleavage of the egg in Laura seems to resemble that in 

 Balanus. The Nauplii of Laura 

 show very little similarity with V 

 the typical Cirripede Nauplius, 

 on account of the absence of 

 the very characteristic frontal 

 horns. A small form observed 

 by Lacaze-Duthiers, and no 

 doubt representing a stage in 

 the course of development of 

 Laura, may possibly be regarded 

 as a complemental male. The 

 Cypris stages of Dendrogaster 

 (Fig. 110), however, are known 

 {Knipowitsch, No. 47), the 

 metamorphosis in this form 

 appearing to be abbreviated, no 

 free Nauplius stage being passed 

 through. The larva, in which 

 an anal aperture, as in the adult, 

 is wanting, bears a general re- 

 semblance to the Cypris stage 



of the Cirripedia. Both the single and the compound eyes are, however, 

 wanting. A very large olfactory filament {a') is developed on the first antenna. 

 There are five biramose pairs of thoracic limbs ; the first abdominal segment 

 carries the rudiment of a penis (p). The abdomen, (ab) which is distinguished 

 by its length, consists of five joints and the furcal appendages. 



Fig. 110.— Free-swimming Cypris stage of Dendogaster 

 astericola (after Knipowitsch). a', first antenna ; ab, 

 abdomen ; d, intestine ; m, buccal cone ; n, nervous 

 system ; p, rudiment of penis. 



E. The Morphological Derivation of the Complemental Male. 



The sexual differentiation of the Cirripedia is very complicated 

 and difficult to explain. As a rule the Cirripedia are hermaphrodite. 

 We shall not err if, considering the almost universal separation of 



