Confidence: I'm as sure as I can be.
Notes: A part of the female frog which is regularly avoided by a certain predator or predators the identity of which I am unsure of. Possibly heron, otter or fox. This is often found at spawning time at spawning sites on moorland lakes I fequent. The large blobs of jelly which would ultimately have encased the ova is very often found with the above structure and ova. Unfortunately not on this occasion. There are plenty of other observations of it on ispot where ova identical to the above can be seen with the jelly. A good example is linked below.