March 3, 1899.] 



SCIENCE. 



313 



trophy in others. Thus, the somatic sen- 

 sory is represented only in the V and X 

 nerves and the visceral sensory in the typ- 

 ical branchiomeric nerves, X, IX, VII. 



Now when in course of vertebrate evolu- 

 tion specialized sense organs appear in ad- 

 dition to the two primary components, their 

 nerves and intra-crauial centers will appear 

 sporadically, depending upon the distribu- 

 tion of the specialized sense organs in ques- 

 tion. These nerves will in general follow 

 the courses of the previously existing so- 

 matic or visceral nerve trunks wherever 

 possible, hence the formation of complex 

 nerve trunks containing several of the com- 

 ponents. Each of these cenogenetic systems 

 of sense organs, like the palingenetic sys- 

 tems, tends to be related to a single intra- 

 cranial center. At present we may enu- 

 merate the following such systems : 



1. Taste buds related to the fasciculus 

 communis (f. solitarius) and its associated 

 nuclei, the chief vagus nucleus (lobus vagi 

 of fishes) . 



2. Terminal buds of the outer skin ; ter- 

 minal relations as in the last case, plus in 

 some fishes the lobus facialis. 



3. Lateral line organs, or neuromasts, 

 related to the tuberculum acusticum and 

 cerebellum, plus in some fishes the ' lobus 

 linese lateralis.' 



4. Ear; central connection as in the last 

 case. 



5. Eye ; related to the mesencephalon. 



6. Nose; related to the primary prosen- 

 cephalon. 



7. Pineal organ ; related to the dien- 

 cephalon ? 



Diagrams were exhibited illustrating the 

 actual relations of these components as de- 

 termined bj'' reconstruction from serial sec- 

 tions in the bony fish, Menidla; and em- 

 phasis was laid upon the necessity of taking 

 these qualitative differences in the nerves 

 into account before trying to work out their 

 metamerism. 



The Maxillary and Mandibular Breathing 



Valves of Teleost Fishes. Uleic Dahlgeen. 



The discovery of a pair of membranous 

 valves placed just inside of the teeth and 

 working automatically to prevent water 

 from leaving by the mouth while they per- 

 mit its free entrance, has enabled the act 

 of breathing in fishes to be clearly described. 

 These valves complete the pump-like struc- 

 ture of the oral cavity, the other pair, or 

 posterior valves, being the branchiostegal 

 membranes. 



In breathing, but two muscular forces 

 must be applied, one to expand the oral 

 cavity by moving the opercular frames out- 

 ward and another to contract the oral cav- 

 ity by moving them inward ; when expand- 

 ing, water comes in through the mouth, 

 being prevented from entering through the 

 gill clefts by the branchiostegal membranes, 

 which act automatically and independently 

 of and contrary to the opercular frames to 

 which they are attached ; when contracting, 

 water is forced out of the gill clefts, but is 

 prevented from leaving through the mouth 

 by the valves in question, which act automat- 

 ically. While breathing, it is true, the fish 

 opens and shuts its mouth somewhat, but 

 this is due not to its effort to prevent a 

 regurgitation of the respiratory stream, but 

 to the relation of its mandible to the oper- 

 cular frames. 



When the valves are cut, the fish is com- 

 pelled to use muscular force to prevent re- 

 gurgitation. 



On the Early Development of the Catfish (^No- 

 turus). F. B. SUMNEK. 



1. No horizontal cleavage takes place till 

 the 64-cell stage or after, and, when it oc- 

 curs, does not result in a definite two-layered 

 condition of whole germ- disc. 



2. The blastomeres resulting from the 

 early cleavages retain their continuity with 

 the protoplasmic network of the j'olk. No 

 sharp line of separation, such as Sobotta, 



