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introducing water into it : but tin- n fir row calcareofis covering 

 which partially confines this tube, preventing dilatation, milil 

 strongly against this hypot he>is. IH)rbign\'- guess seems more 

 reasonable, that tliis lube may not only serve ;is :ii' attachment. 

 luit that it may also asM>t in the formation of a ne\v septum, by 

 keeping filled wit h compressed air the vacant space, in the rear of 

 the animal, which is to be divided oil'. .Prof. Keferstein. of (iot- 

 tingeii. supposes, also, that the Xanfilnn r<>ni/>///n.<. in order to 

 raise itself in its shell to the place where it designs con>t ructing 

 a new partition, employs the tension of an aeriform tlnid. which 

 it produces from the bottom of its sack, and which presses it> 

 body upward. The air disentitled iiy the Nautilus develoi 

 <-ou>,i(lei'able force, because it conquers not only the resistanct- of 

 weio-ht of the animal itself, but also that of the weight of about 

 six atmospheres, which presses upon it in its habitual station at 

 the bottom of the sea. 



In the Report of the Brit. Assoc. for ]si;4. Harry Seely s* 

 " On examining a JVaM^ug-shell, two large muscles are seen (<> 

 have been placed in the lower part of the body-chamber, and 

 connected round the involute spire by a narrow muscle an 

 arrangement to which the shell may owe its involute form. I>e- 

 neath the muscles are the liver, which overlaps the spire, the 

 ovaries, which abut on a lar^e part of the septum, and certain 

 digestive organs above these. lie fore any new chamber can be 

 made, the ^hell-muscles must have moved forward : and before 

 any increase in the ovaries can take place, a place must be formed 

 behind. As the animal steadily grows, all its <rg:m> would 

 enlarge: and, with each successive brood, the distended ovaries 

 would require more space. There is a similar gradual inci 

 in the si/e of the a i r-cha mbers. and, since the development of OT8 

 would necessitate a forward growl h of the mollusk. t lie disci 

 of t lie ovaries would leave an empty space behind, into which t he 

 animal could not. retire, which would then be shut, oil' by a ->ep- 

 tum moulded on the animal's body. I n t he male AV////////.<. t he 

 totes are placed in exactly the same position as the o\arie> of 



the female, and, excepting the liver, form the large-si organ in the 

 inxlv. it may therefore be concluded, that the development of 



the male or-ans would produce results similar to those in tin- 

 other sex ; and likewise end in the formation of chambers. 



