AEACENIDA 



261 



FIG. 51. Upper third of the body of Pentastoma 

 denticulatum. Original. 



The fourth is the sexually-developed stage, furnished with a 

 simple hook-apparatus, and without integumentary denticles. 

 " Our Pentastomes, there- 

 fore/' says Leuckart, " ex- 

 hibit two kinds of larval 

 forms, an earlier and later 

 one, such as takes place 

 in other animals ; this also 

 occurs even in insects 

 (Strepsiptera and Meloidce), 

 only that, in our case (i. e. 

 in Pentastoma}, both do 

 not immediately follow one 

 another, but are separated 

 by a resting condition, 

 which I have designated 

 as the pupa stage. In 

 choosing this name I do 

 not mean to express a complete identity of this intermediate 

 state with the pupal sleep of insects." 



So far as my own observations extend, the pupa, in its later 

 stages, closely resembles the free larva ; but, as Leuckart points 

 out, the earlier stages are very different. The embryo, after 

 encystation, repeatedly casts its skin, and during the intervals 

 of these several successive moultings, the young animal makes 

 rapid growth, accompanied by a series of structural changes. 

 Passing through these it at length acquires the perfected larval 

 state (P. denticulatum). 



As regards the occurrence of this entozoon in the human 

 body, the best account is that given by Frerichs. As quoted 

 in my previous work from Murchison's edition of Frerichs' well- 

 known clinical treatise, the German savant remarks : " The 

 Pentastoma is a parasite which has only recently been dis- 

 covered in the human subject, but it is, nevertheless, far more 

 common in the human liver than the echinococcus. It is 

 devoid of clinical importance, because it does not give rise to 

 any functional derangements. Pruner ('Krankheit des Orients/ 

 1847, s. 245) was the first who pointed out the existence of the 

 Pentastoma in the human liver. On two occasions he found an 

 encysted parasite in the liver of negroes at Cairo, the nature of 

 which, however, he did not accurately determine. Bilharz and 

 Von Siebold (' Zeitschr. fur Wissench. Zoologie/ Bd. iv, s. 63) 



