128 ZOOLOGY 



asexual life cycle as rods, but at the onset of spore formation they 

 decrease in size and numbers. In the spore no mitochondria can 

 be seen, but they reappear in the sporozoite as soon as it is liberated. 

 Horning believes them to be reformed de novo, and therefore that 

 they have ceased to exist as individual inclusions during the spore 

 stage. This is of course possible, but we do not think that the 

 technique for demonstrating mitochondria is sufficiently advanced 

 for us to be able to say that because they are not visible they have 

 entirely disappeared as cell inclusions. Theoretically, of course, 

 such a statement can never be justified, although the presumptive 

 evidence may be very strong. Such evidence is not really forth- 

 coming, however, in this case. The lapse into small spheres of 

 small staining capacity may here be more emphasised than in the 

 case of the sj^herical bodies of Opalina cysts, but both appear to 

 be correlated with the small metabolic activity as Horning sug- 

 gests, and there does not seem to be sufficient justification for 

 assuming that the mitochondria disintegrate in one case and not 

 in the other. 



To return to the previous point regarding the function of the 

 mitochondria ; it would seem that the evidence of Horning in 

 Amoeba leaves little doubt that the suggestion that the mito- 

 chondria are the seat of enzymatic activity must be taken seriously. 

 On the other hand, a great deal of negative evidence is forth- 

 coming. For instance, Cramer and Ludford have shown that the 

 process of fat absorption in the mammalian intestine is associated 

 with a hypertrophy of the Golgi apparatus, but the mitochondria 

 remain unchanged throughout the cycle (23). The same two 

 workers, however, in the case of the thyroid gland, note that both 

 Golgi and mitochondria are enlarged during secretion (Fig. 60). 

 Their figures show, and they write of, an enormous enlargement of 

 the mitochondria, accompanying a convolution of the Golgi 

 apparatus (24). They give as an explanation that the Golgi 

 apparatus is probably actively engaged in the actual production 

 of the secretion, but that the mitochondrial variations produce 

 corresponding variations in surface energy within the cytoplasm, 

 and thus effect redistribution of the lipoids. If this were the whole 

 story one might be excused expecting similar j^henomena in the 



