it is possible to find almost all transitions between the typical vagina accord- 

 ing to Odhner and ductus vaginalis. Because of this we have no right to con- 

 sider these formations as not homologous and consequently Odhner's point 

 of view also appears to be erroneous. The receptaculum seminis occurs 

 among representatives of all groups of monogenetic trematodes. Often how- 

 ever it is also absent. It represents a special widening which serves for 

 the retention of sperm and its location is varied. Sometimes it is simply 



a widening of the oviduct. In a number of speclesthe receptaculum seminis 

 lies along the vaginal duct or is even functionally replaced by widening 

 sections of the latter. There are no designations for the various types of 

 receptacula seminis -, however, one must recognize the receptaculum 

 seminis oviducti and the receptaculum seminis vaginalis as not homologous 

 formations. 



The obtype into which the ductus communis passes represents 

 the place of the formation of the eggs. Usually it is powerfully developed 

 and separated from the duct which opens into it and also from the uterus, 

 if the latter exists, by powerful sphincter-shaped muscular fibers. The 

 form of the obtype varies, it can be rounded, egg-shaped, pear-shaped, 

 etc., which basically corresponds to the shape of the egg which is formed 

 therein. This ootype can be considered as an odd-shaped mold for the 

 "stamping" of the eggs. Into it open numerous monocellular glands called 

 shell glands or Mehlis' glands. Among a majority of species they are sharply 

 developed and often divided into two groups which are variously colored on 

 the slides. This can be observed with special clarity among Polystoma 

 integerrimum Froelich. The function of these glands is not completely clear 

 (for more details on this see pages 85 and 87 ). 



Among a number of Monogenoidea the ootype opens directly into 

 a sex cloaca and the egg which is formed passes from the obtype, after a 

 certain period of time, into the surrounding nnedium without prolonged delay 

 in the body of the parasite. In other forms a more or less long uterus, which 

 contains the fully formed eggs for a certain time, starts from the obtype. In 

 such a fashion among some forms, the ob'type functionally serves as the 

 uterus and in other types as both. One must note that this peculiarity does p. 73 

 not have important phylogenetic significance. Apparently the absence of the 

 uterus is a primary phenomenon but among a number of forms, even highly 

 organized ones, there is only an obtype. It is interesting that, during the 

 time of embryological development of Polystoma integerrimum the so-called 

 "gill form" has only an obtype, whereas the form from the urinary bladder 

 of the frog has a well-developed uterus (see page 185 ). 



The uterus can be of variable length from comparatively short 

 to very long and very curved and in a majority of species its curves lie 

 across the body and only in Chimaericola are located longitudinally (Fig. 

 107). Among many forms the uterus is sac -like. Characteristic among 

 some is the distribution of the eggs in a packet, whereas among the 



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