222 J. A. MYERS 



Rein, G. 1882 Untorsiichungen liber die enibryon:ile Entwicklunf^sgeschichte 



der Milchdriise. Arehiv fiir mikr. Anatomic, Bd. 20 and 21. 

 Ru(;e, G. 1895 Die Hautmusculatur der Monotremen und ihre Beziehiingen 



zu dem Marsupial- und Mammarapparate. Semon's Zool. For- 



schungsreisen, Bd. 2 (Jenaische Denkschriften, Bd. 5). 

 ScHiCKELE, G. 1899 Beitriige zur Morphologic und Entwickelung der normalen 



und i'lberzilhligen Milchdriiscn. Zeitschrift f. Morphologic und 



Anthropologic, Bd. 1, Heft 3. 

 ScHiL, L. 1912 Recherches sur la glandc mammairc, sur les phases qu'elle 



prcscnte au cours de son evolution ct Icur determinismc. These, 



Lyon. 

 ScHULTZE, O. 1892 Ueber die erste Anlage des Milchdrlisenapparates. Anat. 



Anz., Bd. 8. 



1893 Beitrag zur Entwicklungsgeschichte der Milehdriisen. Ver- 



handl. d. phys. med. Gcsell. in Wurzburg, Bd. 26. 

 SoBOTTA, J. 1895 Die Bcfruchtung und Furchung des Eies der Maus. Archiv 



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wcissen Ratte. Anat. Hefte, Bd. 42. 



PLATE 1 



EXPLANATION OP FIGURES 



7 External view of a wax model reconstructed from the right first thoracic 

 gland of an albino rat fetus of fifteen days and nine hours. X 100. e.s., emi- 

 nence (mammary hillock) on surface of skin produced by developing mammary 

 gland. 



8 External and part of internal view of a wax model reconstructed from the 

 left first inguinal gland of a female albino rat fetus of eighteen days and nine 

 hours. X 50. n.p., depression representing mammary pit; p.d., primary duct 

 anlage. 



9 External view of a wax model reconstructed from the left second inguinal 

 gland and surrounding region of a female albino rat fetus of twenty days and 

 six hours. X 50. n.a., nipple anlage; n.p., mammary pit; s., sulcus surround- 

 ing nipple anlage. 



10 Internal view of a wax model reconstructed from the right first thoracic 

 gland of an albino rat fetus of fifteen days and nine hours. X 100. m.a., ellip- 

 soidal mass of cells (mammary gland anlage) connected to epidermis through a 

 constricted neck (nk). 



11 Internal view of a wax model reconstructed from the right abdominal 

 gland of a female albino rat fetus of eighteen days and nine hours. X 50. e.b., 

 end-bud; p.d., primary duct; s.d., secondary ducts. 



12 Internal view of a wax model reconstructed from the left first inguinal 

 gland of a female albino rat fetus of twenty days and six hours. X 50. e.b., 

 end-bud; ep.in., epithelial ingrowth (hood); p.d., primary duct; s.d., secondary 

 duct; t.d., tertiary duct. 



