PLATE VI. 



Fig. x. — Ventral view of Van der Hoeven's organ. X 2. 



L, vertical lamina'. 



N, nerve. 



VF, vertical Assure. 



W, wall of the pocket, or atrium, into which the anterior end of the organ projects cut from its attachment to 



the organ and folded to one side 

 1, 2, 3, muscles of the organ. 

 Fig. 9. — Longitudinal section of Van der Hoeven's organ, takeji through the median vertical fissure. (The ventral 

 side is uppermost. ) X 2. 

 (i, (i, glandular portion of the organ. 

 HF, horizontal fissure. 

 L, horizontal laminae. 

 Fig. 10. — Cross section of Van der Hoeven's organ taken just back of the middle of the organ. iThe ventral side is 



uppermost.) X -. 

 Fi«. 11. — Shell of Nautilus pompilius. \ natural size. 

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