OCTOBEE 16, 1908] 



SCIENCE 



519 



Dr. Holland says that he knows of no other 

 opening through which the auditory nerve 

 could escape from the brain cavity; but un- 

 fortunately he did not think it necessary to 

 indicate the distribution of this nerve. 



The writer knows of no fossil skull that is 

 better fitted for section than the one described 

 by Director Holland. Had it been divided 

 along the median plane and had the matrix 

 then been removed, much valuable informa- 

 tion would have been secured. Probably 

 some sutures that do not show on the rough 

 outer surface would reveal traces of them- 

 selves on the inner surface; and important 

 suggestions regarding some of the foramina 

 would offer themselves. Especially, it would 

 then be possible to obtain a complete cast of 

 the brain-cavity of this interesting dinosaur. 



Two long splints of bone which extend from 

 the premaxillse to the front of the external 

 nares, joining along the midline, were sup- 

 posed by Marsh to be processes of the pre- 

 maxillffi. Dr. Holland regards them as dis- 

 tinct bones and suggests that they are the 

 lateral ethmoids. It would be interesting to 

 learn how the lateral ethmoids could migrate 

 from the prefrontal region and come to lie 

 on the midline in front of the nostrils. It is 

 very doubtful whether the splints are distinct 

 from the premaxillse. 



The bone called the presphenoid by Dr. 

 Holland is the parasphenoid. 



As is well known, the nostrils of Diplo- 

 docus lie far toward the rear of the skull, be- 

 tween the orbits. On each side of the face, 

 far in front of the orbits, there is found a 

 fontanel in each maxillary bone. This opens 

 into the cavity above the pterygoid bones. 

 Dr. Holland suggests that these openings 

 were probably a pair of supplementary nos- 

 trils. From what we know about the devel- 

 opment of the rectum it is imaginable that a 

 nasal passage might divide into two passages, 

 and that one of these might remain in its 

 place while the other, with its external open- 

 ing, might migrate to where we find it in 

 Diplodociis. But had this happened in Dip- 

 lodociis the nostril that retained its primitive 

 position would be represented by one of the 

 two clefts found near the midline at the 



front of the long premaxillary splints al- 

 ready mentioned, which clefts, as Dr. Hol- 

 land says, opened into the nasal passages. 

 If then the maxillary fontanels were also sup- 

 plementary nostrils, we should have an animal 

 with three pairs of nostrils. As to those in 

 the maxillae, it would, I think, be difficult to 

 explain their morphogeny. We must certainly 

 look on the proposition as a fanciful one. 

 I see no reason to doubt that the fontanels 

 in the maxillse were in life filled with connec- 

 tive tissue and covered over by the skin. 



In a foot-note Dr. Holland informs us that 

 certain groups of reptiles have no external 

 ears and that Diplodocus probably lacked 

 these organs ; but we should like to know what 

 reptiles do have external ears. 



In nearly all of Dr. Holland's references to 

 the two skulls of Diplodocus in the U. S. Na- 

 tional Museum he gets the numbers 2672 and 

 2673 exchanged. Apparently only the refer- 

 ence on page 239 is correct. On page 235 he 

 credits to the TJ. S. National Museum two 

 specimens that are in the American Museum 

 of Natural History, New York, Nos. 545 and 

 969. Oliver P. Hay 



THE SPREADING OF MENDELIAN CHARACTERS 



The point made by Mr. Hardy in his note 

 on " Mendelian Proportions in a Mixed Popu- 

 lation " in Science of July 10, 1908, is a very 

 important one, though it is open to a danger- 

 ous misunderstanding. What Mr. Hardy 

 gives us is a mathematical proof that under 

 the assumptions of Mendelian inheritance a 

 dominant character does not tend to spread or 

 a recessive character to die out. A strictly 

 Mendelian character would not tend either to 

 increase or diminish its representation in a 

 species, unless favored or opposed by selection. 

 This is a mathematical confirmation of the 

 biological evidence that Mendelism has no re- 

 lation to evolution. 



Nevertheless, the proviso of strict Mende- 

 lian inheritance robs the demonstration of a 

 truly biological significance and forbids us to 

 rely on it as a protection against the spread of 

 brachydactyly or other abnormal characters in 

 man himself or in our domesticated plants and 



