studies on marine Oslracods 



77 



It seems to me very probable for several reasons that the penis is of the nature of a 

 limb, as has been assumed by several investigators; I need only point out here the great resem- 

 blance this organ bears to a biramous limb in those forms in which it is characterized by a very 

 simple structure, e. g. Asterope, Philomedes, (cf., for instance, G. W. MOller, 1894, pi. 5, fig. 41) 

 and that it is innervated in the same way as other limbs. 



First antenna: — This antenna would have had eight joints. The only 

 reason for this assumption that I am able to find in G. W. MtlLLER's work is that this 

 number is the largest that is observed in all the known O s t r a c o d s, „wir finden 

 diese Zahl als hochste bei den Podocopa und Myodocopa''. It seems to be impossible to accept 

 this reason as in any way decisive. From the point of view of the theory of evolution one can 

 of course equally well imagine a cleavage of joints as a union of them. Embryology does not 

 support this assumption at all, nor does comparative anatomy. The only resemblance between 

 this limb of a C y p r i d and a C-y p r i d i n i d is really the number of joints. Both the 

 equipment of bristles and the musculature are so profoundly different that they do not seem 

 to indicate that the different joints of this antenna in one group are homologous with the corre- 

 sponding joints in the other. 



The same uncertainty applies to the assumption that this antenna was originally a sensory 

 and a locomotory organ at the same time, ,,vielleicht glich sie am meisten der 1. Antenne 

 der Cypridinide n". According to the theory of evolution there can scarcely be any 

 reason against an assumption that even a first antenna that was originally used exclusively 

 as a locomotory organ might gradually develop as a sensory organ and vice versa. It may be 

 pointed out that among the H a 1 o c y p r i d s, in the majority of which the first antenna is 

 exclusively or almost exclusively a sensory organ, the genus Thaumatocyprv,', which in many 

 respects is to be considered as the most primitive, has a first antenna which, as far as one can 

 see, serves exclusively or practically exclusively as a locomotory organ. As is seen above, 

 G. W. MUller assumes that during the course of development sometimes one and sometimes 

 the other of these two functions has dominated. 



In my opinion it is impossible at present to give an opinion with any great degree 

 of certainty as to the type of this limb in the Protostracods. 



Second antenna: — It seems to me probable that the protopodite of the 

 second antenna in C y p r i d i n i d s. Halo c y ji rids and P o 1 y c o p i d s is composed 

 of at least two joints; traces of the original boundary between two joints have presumably 

 been observed by G. W. MCller in the Polycopids (1894, p. 39). On the other 

 hand this author's view with regard to the protopodite in other forms seems to me far 

 less probable. 



In an article ,,M i 1 1 h e i 1 u n g e n ii b e r C o p c p o d o n", 1893, W. GlESBRECHT 

 wrote as follows (p. 86) with regard to the maxilliped of the Copepoda: ,,Da6 Glieder miteinander 

 verschmelzen und die Gliederzahl sich auf diese Weise vermindert, laBt sich hiiufig nachweisen; 

 aber wie Glieder verschwinden konnen, zumal relativ so umfangreiche und muskelerfiillte und 

 so niitzliche wie die Basalia, das hiitte Clals doch irgendwie dem Verstiindnis des Lcsers naher 

 bringen miissen" . . . etc. However much ope nto criticism this statement may be, I should 



Penis 



First antenna. 



Second antenna 



