1916.] NATURAL SCIENCES OF PHILADELPHIA. 



the two daughter cells arising from the division of a sporo lasl do 

 not, always take on the oval form of the mother cell, but each r< tai 

 the form it had at the momenl of division and does no1 again divide. 

 The division of the sporoblast having been longitudinal, the form of 



the daughter cells is that of a banana and they are, in fact, the spori 



The production of the spores in this way is initiated in the central 

 part of the cyst. At the outset of this new line of development, the 

 cysts will contain many sporoblasts and few spores and there is no 

 doubt that the production of both spores and sporoblasts may take 

 place simultaneously in different or even the same parts of the same 

 cyst. Eventually, however, the divisions of the sporoblasts produce 

 only spores which finally come to be the only elements present 

 within the cysts. 



Bertram (1892) describes very early stages of the evolution of 

 Sarcocystis tenella in the muscles of the sheep. Several of his original 

 figures have been reproduced in most of the general works on the 

 parasitic Protozoa, and doubtless are familiar to all students of thes< 

 organisms. Of these, Bertram's figure 22, reproduced by Doflein 

 (1911) as figure 891 C, page 922, represents an element 47 /-* long by 

 6 /j wide. We have here what appears to be a solid body indistinctly 

 marked out into small round or oval elements, each with a nucleus, 

 It is strikingly like the smallest stage of Sarcocystis muris a- figured 

 and described by Negri. 



Bertram also figures somewhat larger stages of the muscle phase of 

 Sarcocystis tenella, and in these, reproduced by Doflein (1911) as 

 figures 891 B and D, page 922, the so-called cysts are more or less 

 completely differentiated into rounded or oval nucleated cells, the 

 sporoblasts. 



Since the Sarcosporidia are always classified as Neosporidia, it has 

 been tacitly assumed that the earliest stage in the muscles must be 

 an organism in which growth and spore formation take place coinci- 

 dently. The very smallest stages figured and described by Negri 

 and Bertram are capable of being interpreted in this way, since they 

 appear to consist of bodies of some size, indistinctly divided into 

 rounded or oval nucleated elements. Inasmuch, however, as these 

 bodies occur embedded in the muscular tissues of their host-, p 

 by no means easy to get clear-cut pictures of them, and it is whol Im- 

 possible that the rather indefinite appearances figured by these two 

 authors may be due merely to the difficulty of differentiating the 

 sporoblasts from the surrounding host tissues. In consequence, it 

 is not at all impossible that these earliest stages of Bertram and 



