446 CRUSTACEA MALACOSTRACA. 



until its death. In the Hermit Crab, Eupagurus, on the other 

 hand, ecdysis is continued, and growth may even (as in capons) 

 be accelerated by the presence of the parasite. The effects 

 of the parasitism, on the hosts, are manifold. In the first 

 place it leads to a more or less complete atrophy of the gonads, 

 out of all proportion to the effects on the other organs of the 

 body. 



A further effect is apparent in the modification of the secondary 

 sexual characters of the host. In the case of the female hosts 

 these characters may undergo reduction. Thus in the females 

 of a Crab, Inachus, affected by Sacculina, the swimmerets 

 which appear at the last moult, and especially their ovigerous 

 endopodites, are reduced in size. In the males, not only are 

 the secondary male characters, the copulatory styles (first ab- 

 dominal appendages) and chelae, reduced in size, but there 

 is a definite assumption of female characters in addition (Fig. 

 281). Thus it has been found that there is a tendency for 

 the infested males to become hermaphrodite. In Inachus the 

 abdomen becomes longer and broader, the posterior abdominal 

 swimmerets (3-5), which have disappeared since the later larval 

 (Megalopa) stages, grow again, and even, in some cases in which 

 the gonad is not completely aborted, it is found to develop 

 ova as well as spermatozoa, although, owing to the occlusion 

 of the ducts, the products can never be shed. 



Results similar to those in Inachus have been obtained by 

 Smith in Pachygrapsus, and Potts has found that Eupagurus 

 meticulosus, infested by Peltogaster, exhibits similar effects though 

 in a more pronounced degree. Potts concludes that in this species 

 ova are developed in the gonads of all infected males, after the 

 parasite has become external. For further details on these 

 striking results the reader is referred to the original memoirs.* 



Development. The eggs of some groups of the Malacostraca 

 pass through their development in the brood space of the mother, 

 being contained either between the thoracic legs and protected 

 by the lobes of the shell (Leptostraca) or between the oostegites 

 and the ventral wall of the thorax, as in the Cumacea, Isopoda, 

 Amphipoda, Chelifera, and the Schizopod families, Lopho- 



* See too the recent botanical work by Strasburger, Versuche mit 

 diocischen Pflanzen in Rucksicht auf Geschlechtsverteilung, Biol. Cen- 

 tralblatt, T. xx (1900), p. 689. 



