35^ FROM FISH TO PHILOSOPHER 



Effect of feeding meat on metabolic rate. Journal 

 of Cellular and Comparative Physiology, 6: 335. 

 1935. 



Romer {yy} erected the subclass Choanichthyes 

 (choana = funnel; ichthys = fish) to include the Dipnoi 

 and Crossopterygii, this name being based upon the 

 presence of internal nostrils (funnels) leading from the 

 mouth to the exterior, a feature that was once supposed 

 to be a sign of aerial respiration. This taxonomic cate- 

 gory is equivalent to Hubbs's earlier Amphibioidei, but 

 neither includes the air-breathing, Paleozoic Osteich- 

 thyes. There is, therefore, no satisfactory taxonomic 

 category to include all the air-breathing fishes, both 

 Paleozoic and recent. Atz {74} has recently shown that 

 none of the surviving lungfishes uses the internal nos- 

 trils for this purpose; rather they gulp air through the 

 mouth, as do many other fishes that supplement their 

 gills with aerial respiration but do not possess internal 

 nostrils. The passages serve only as olfactory organs and 

 there is no reason to suppose that they served a respira- 

 tory function in the Devonian fishes. In the recent Am- 

 phibia the internal nostrils are used for respiration, but 

 Atz, citing an opinion of Romer's, believes that this res- 

 piratory function was acquired in the transitional Cros- 

 sopterygii or early Amphibia. 



Studies on the lungfish, Protopterus aethiopicus, have 

 been reported by the writer {80, 81, 83, 84}, and the cir- 

 cumstances attending the collection of the fish in Africa 

 are narrated in Kamongo {82}. 



In the Paleozoic ganoid fishes, the scales, only a step 

 removed from the armor of the placoderms, were com- 

 posed of an inner layer of bone and an outer layer of an 

 enamel-hke substance, ganoin, and perhaps the close 

 mosaic of these scales precluded the presence of the 

 mucous glands, so important in the estivation of Pro- 

 topterus. Lepidosiren, which estivates, secretes mucus 



