186 



SCIENCE. 



[Vol. II., No. 28. 



organ opening into the mouth, or else a glan- 

 dular organ opening into the mouth." It seems 

 to me that the facts of its development in Pe- 

 tromjzon negative this hj-pothesis. It is there 

 seen to have no connection with the mouth ; 

 nor is this mode of development so entirely' 

 exceptional as it would at first seem. Of all 

 known embrj'os of craniate vertebrates, the 

 lamprej' has perhaps the smallest brain and 

 the least cranial flexure ; which state of things 

 allows space for a distinct invagination from 

 without to reach the infundibulum. In the 

 Amphibia this is seen to a less degree : the 

 invagination for the 

 pituitar}- bod}- is 

 formed before the 

 appearance of the 



Fig. 4. — Section thro' 



, heiul of embryo of 



Bombinator (.tfter 



Gtitte) . Letters as 



before. 



Fig. .5. — Section thron.ffh bead of 

 young tadpole of Bombiii:itor 

 (.nfter Gijtte). Letters ae be- 

 fore. 



mouth, and just above it ; so that, when the 

 mouth appears, the two have an apparent con- 

 nection, being crowded together b}- the in- 

 creased cranial flexure. In other tj-pes — such 

 as the selachian, bird, mammal, etc. — the 

 brain acquires a very great size in early em- 

 br30uic stages, and the cranial flexure is con- 

 sequently very much increased. In these cases 

 almost the only possible wa}- for an epiblastic 

 invagination to reach the infundibulum is from 

 the epiblast of the mouth. If the reader will 

 compare the figures given above for the 1am- 

 prej- with those from Gotte (figs. 4 and 5) for 

 .the amphibian and that from Balfour for the 

 selachian (fig. 6), these progressive changes 

 will at once be clear. Ifem- 

 bryological evidence counts 

 for any thing, it would there- 

 fore seem extremeh' proba- 

 ble that the connection of 

 the pituitary- body with the 

 Fig. 6.— Section thro' mouth is Only a sccondary 

 PrUtinra8"'(,Se°r One, brought about by the 

 Balfour), fetters greatly increased cranial 

 *" "''^' flexure in the higher types. 



Assuming that the invagination originally took 

 place independently of the mouth, such a sec- 

 ondary connection would be almost a mechani- 

 cal necessity- of the great brain-growth. 



Now, while I am not prepared to follow 

 Dohrn in maintaining that the entire blind 

 nasal sac below the olfactory capsule of Pe- 

 tromyzon really belongs to the pituitarj- body, 

 yet I quite agree with him that the connection 

 of the pituitary- body with the olf:\ctory organ 

 is a secondary one. I have, in a former paper, 

 stated the reasons for believing that the un- 

 paired condition of the olfactory organ in the 

 Cyclostomata is not primitive, but secondary, 

 caused by the coalescence of two originally dis- 

 tinct pits. Now, if thei-e were an indei)endent 

 invagination in the median line of the head, 

 the causes which brought about the union of the 

 two nasal sacs would also cause the latter to 

 coincide with the pituitary involution. This 

 is just what I conceive to have happened. 



If the above reasoning be correct, the fact 

 would seem clear, that the pituitary body is the 

 remnant of some originally- independent organ, 

 which opened, not into the mouth, but on tiie 

 surface of the head. Almost certainly (his 

 organ belonged to the invertebrate ancestor 

 of the vertebrates. What its function was, is 

 a difficult problem. Dohrn's h3-pothesis that 

 it was formed bj- the coalescence of a pair of 

 gill-clifts is untenable, not onlj- for the reasons 

 already given, but on account of the invariable 

 epiblastic origin of this organ, while gill-clefts 

 always arise in the vertebrates as outgrowths 

 of the hypoblast. Perhnps we may modify Bal- 

 four's suggestion, and assume tentatively that it 

 was a sense organ or gland which, having lost 

 its function, has become I'udimentarj'. At all 

 events, it will be a step gained if we can estab- 

 lish the fact that the pituitary body is an oi'gan 

 originally independent both of the mouth and 

 of the olfactory apparatus. W. B. Scott. 



Morphological laboratory, Princeton, N.J., 

 July 5, 18S3'. 



THE WEATHER IN JUNE, 1S8S. 



The monthly weather review of the U. S. 

 signal-service contains in usual detail reports 

 from all portions of the country of the weather 

 conditions which characterized the month of 

 June. There were no unusual meteorological 

 features ; the month exhibiting the ' average 

 weather,' as far as this term can be realized. 

 The destructive floods in the lower Missouri 

 River, and in the Mississippi River between 

 St. Louis and Cairo, the unusual rainfall in 

 that section, and severe local storms in many 

 of the states, are the special events of note. 



The mean distribution of barometric press- 

 ure is illustrated hy the accompanjing chart, 

 which also contains the mean isothermal lines, 



