PEOF. W. A. HASWELL OX AUSTRALASIAN POLTCLADS. 477 



are nuQierous spermatozoa, eatirely absent in other parts. Moreover, in the adjoining 

 part of the lumen, and in that part alone, there are numerous spermatozoa. The long 

 narrow body is found, Avlien examined under a high power, to consist of a strand of 

 globules of prostate secretion, or something indistinguishable from it in appearance, 

 mixed with spermatozoa. Its entire length is roughly about 06 mm. 



There can be little doubt that we have here to do with a wound inflicted by the 

 formidably armed penis. The copulating individuals were applied together by their 

 ventral surfaces, the corrugated areas acting like the suckers of the Cotylea, as organs 

 of adhesion, when the penis of the one was driven in through the mass of tissue 

 surrounding the lumen of the vagina, nearly penetrating as far as the latter. The 

 spermatozoa and prostate secretion were then discharged and the penis withdrawn, a 

 plug of prostate secretion closing up the wound and thus preventing the escape of the 

 spermatozoa. The passage of the spermatozoa to the interior of the lumen is facilitated 

 by the fact that in the middle region of the vagina there are very few shell-gland ducts 

 passing inwards and perforating the epithelium. 



In another specimen, cut into a series of longitudinal vertical sections, the same thing 

 appears. Here there is a large mass of spermatozoa in the substance of the wall of the 

 vagina, and this is connected with the ventral surface in front of the corrugated area 

 by a narrow cleft filled with prostate secretion mixed with spermatozoa, the plug of 

 this material projecting freely on the surface. But in this case the perforation has 

 actually passed through the epitlielium of the vagina, and in this position a portion of 

 the mass of spermatozoa projects freely into the lumen. 



Such a mode of copulation as this — by perforation of the body-wall in a definite locality 

 — has not been proved to occur in other Polyclads, and is certainly exceptional in that 

 class. Perhaps it may be found to occur in the case of other forms with chitinous penial 

 parts and a thick-walled bursa copulatrix. I have found a similar type of copulation to 

 characterize Prorhynchus (7) and Strut iodrilm (8). 



The ova in the uterus are all in the stage with a centrally placed spindle and, usually, 

 a spermatozoon (rarely more than one) in various phases of transition in the cytoplasm. 

 Echinoplana is apparently more nearly allied to Leptoplana than to any described 

 genus. But it differs in several very important points from the members of that genus. 

 The entire structure of the male copulatory apparatus is Avidely different from what we 

 find in Leptoplana or in any related form. The same holds good of the corresponding 

 parts of the female reproductive apparatus. The complete absence of a reflected or 

 dorsal limb of the vagina is a veiy special feature, and the massive vagina with its 

 unsymmetrically placed anterior diverticulum is as characteristic, in its way, as the penis 

 with its array of teeth. 



IParaplanocera, Laidlaw (15), has a similar diverticulum of the vagina, or, more strictly, 

 has a bursa which is in the form of a muscular diverticulum of the vagina; but it has 

 no other points of resemblance to the form now under consideration, though the penis 

 has small chitinous spines. Paraplanocera has tentacles, an independent prostate, 

 paired vcsiculse, and a reccptaculum seminis. 



Echhioplana may be defined a,s a Leptoplanid without tentacles or marginal eyes. Two 



