1917] Boeck: Mitosis in Giardia microti 19 



ever, completely formed previous to the division of the eentrosomes, 

 but their final separation, after the previous parallel fusion in pairs, 

 came as it does in mitosis of Metazoa, after the eentrosomes had 

 divided. 



The behavior of the blepharoplasts, and axostyle, the distribution 

 of the chromatin in the nucleus, and the influence of the cytoplasmic 

 structures, the eentrosomes afford clear morphological evidence for 

 the correlation of mitotic activity with changes in the cytoplasm. 



Neuromotor Apparatus 



The evidence of the presence of a unified system of structures 

 which may be closely associated with the motor and sensory activi- 

 ties of Giardia was brought forward by Kofoid and Christiansen 

 (1915a, &). They called this system the neuromotor apparatus. 



In Giardia microti this same system appears, and here may be ' 

 briefly described. Figure 1, plate 1, is indicative of what is present 

 in all forms. The neuromotor apparatus may be conceived as consti- 

 tuting here a union of the fibrillar system with the nuclear system. As 

 has been said before, the two nuclei are connected together by rhizo- 

 plasts, which on their route join the eentrosomes and the blepharo- 

 plasts. 



The blepharoplasts together constitute the center of the fibrillar 

 system. Connected to the axostyle are the anterior and posterior 

 peristomal fibrils, the posterolateral flagella by means of intracyto- 

 plasmic portions, then the free ventral flagella, the pair of caudal 

 flagella, and the parabasal bodies. The anterolateral flagella arise from 

 the blepharoplasts. Thus all the fibrillar and motor parts are con- 

 nected directly to the blepharoplasts, or indirectly by means of the 

 axostyle, and, since the blepharoplasts are connected directly with 

 the eentrosomes and nuclei, there exists a definite integration into a 

 single system of both the nuclear and fibrillar structures. The great- 

 est metabolic activity takes place in the cytostomal area, and here we 

 find the neuromotor apparatus conspicuously in evidence by virtue of 

 the continuous fibril (peristomal fibril) bordering this area. This 

 condition is analogous to the condition found in metazoan animals, 

 such as trematodes and cestodes, wherein we find the presence of 

 nerve-rings associated with sucker-like organs of attachment. Because 

 of the close association of this unified system with the areas of motor 

 and metabolic activities, these regions presupposing the existence 

 of structures for the accommodation of motor and possible sensory 



